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GFN Prime Search Status and History

This page summarises the search history for Generalised Fermat Primes b^2^n+1, for all n >= 13 which have been searched. We record all the known primes for each n, along with notes on when each range was searched and by whom. The data has been compiled by Iain Bethune from a range of sources, including the the Top 5000 database, Yves Gallot's GFN Prime Search and PrimeGrid's own records.

It will be periodically updated, especially when new primes are found.

Quick links: n=13, n=14, n=15, n=16, n=17, n=18, n=19, n=20, n=21, n=22

Range status key:

Range has been double-checked

Range is currently being searched

Range has been single-checked

Primes have been reported in this range but the complete search history is unknown

GFN Prime Search Status: n=15

As of 27th July 2018, there are 1014 known primes of the form b^2^15+1 = b^32768+1.

The following values of b give primes:

b	Range status
70906 167176 204462 249830 321164 330716 332554 429370 499310 524552 553602 743788 825324 831648 855124 999236 1041870 1074542 1096382 1113768 1161054 1167528 1169486 1171824 1210354 1217284 1277444 1519380 1755378 1909372 1922592 1986700 2034902 2147196 2167350	Up to b=2.2M was first searched by Yves Gallot's GFN Search. A single-pass check was made using Proth.exe, completed on 21st February 2002. 35 primes were found. A full double-check has been carried out on BOINC by PrimeGrid using Genefer in October 2015.
2279250 2282862 2329148 2351172 2354572 2354618 2435410 2510928 2538626 2585646 2619572 2679502 2696506	The range between b=2.2M and 2.8M was searched by Heuer and Sun (and others?) using Proth.exe between August 2003 and December 2004. 13 primes were found. A full double-check has been carried out on BOINC by PrimeGrid using Genefer in October 2015.
2973894 3000336 3042376 *	The ranges b=2.8M-3M and b=3M-3.1M were reserved by Heuer and Sun respectively, and were are least partly searched using Proth.exe. 2 primes were found. A full double-check on BOINC by PrimeGrid using Genefer found 1 previously undiscovered prime (*) on 23rd October 2015.
3109540 3134838 3149688	3 Primes in this range were found by Ayeni using Proth.exe between April 2004 and April 2005. A full double-check has been carried out on BOINC by PrimeGrid using Genefer in October 2015.
3391432 3394960 3417444 3467622 3472100 3532700 3642296 3664554 3756658 3769892 4004620 4042212 4053566 4108672 4184696 4197530 4323648 4396444 4403010 4465132 4487952 4578290 4698564 * 4826770 4971052 5014954 5042524 5079358 5144952 5177652 5446484 5667050 5761466 6041274 * 6068406 * 6199694 * 6275442 * 6318186 * 6412528 * 6607866 6656034 6700428 6731948 6960350 7039132 7284770 7285278 7510824 7528624 7663846 7680822 7736350 7869772 8010848 8100176 8102494 8106614 8123056 8125520 8157528 8191116 8244666 8273506 8285500 8307368 8345790 8380046 8442162 8461246 8464936 8483782 8635576 8712924 8796286 8883278 9011408 9148556 9214318 9302934 9342420 9458852 9543806 9622594 9693048 9744750 9850652 9863800 9926910 9973932 10021136 10120074 10403098	This range was first tested on PRPNet by PrimeGrid using Genefer, LLR and PFGW from January 2011 finishing at b=10428486 on 18th October 2015 , finding 85 primes. A full double-check has been carried out on BOINC by PrimeGrid using Genefer in October and November 2015. 7 previously undiscovered primes (*) were found during this check.
10448246 10689024 10742748 10758842 10877222 11428394 11600204 11623354 11688764 11741086 11756060 11967372 12007538 12013942 12177788 12500316 12525142 12563092 12825258 12952476 13004344 13062632 13236710 13268134 13421628 13516486 13522632 13526546 13535820 13553636 13649540 13685572 13782404 13984036 14023640 14090140 14212786 14466952 14662858 14805912 14933582 14953270 14996602	Starting in November 2015, PrimeGrid ran a two-pass search on BOINC using Genefer, finding 43 primes.
15079730 15297664 * 15547296	This range was at least partly searched by Siegert using PFGW in 2011, yielding 2 primes. The range was double-checked by PrimeGrid on BOINC using Genefer in December 2015 and found 1 additional prime (*). All b up to 16253972 have been checked as of 23rd December 2015.
15674780 15731584 15800610 15804124 15859134 16217720 16307584 16341644 16391094 16676202 16710646 16715766 16933402 16990688 17132938 17166276 17213996 17255882 17498720 17503170 17630048 17746856 17821911 17914162 17957740 17978924 18027484 18162892 18318176 18376198 18860674 18900442 18930698 18959384 19011418 19045454 19159066 19297056 19353558 19444332 19454016 19510862 19523144 19567100 19587542 19661856 19814292 19864152 19884080 19998404 20009904 20033660 20037206 20190116 20228770 20294998 20507016 20583814 20586806 20607250 20738336 20805908 21080328 21232188 21300678 21411466 21444466 21479990 21510206 21661504 21702126 21950862 22040372 22102946 22155010 22217326 22459694 22574138 22631632 22783708 22799674 22844832 22875794 22996256 23054064 23142958 23171048 23343918 23447300 23544450 23566592 23625178 23717922 23842202 23962732 24057570 24154818 24261684 24264168 24354070 24452630 24607410 24641706 24698156 24710848 24745350 24802522 24811616 24953074 24994852 25013972 25213932 25319642 25339900 25361258 25404726 25521108 25580284 25676304 25676940 25853424 25942142 25980454 26055736 26088376 26195856 26346504 26467316 26621776 26752326 26775424 27021706 27047488 27271312 27285676 27390636 27505842 27525168 27543360 27550814 27843292 27893132 27939240 27958104 28049668 28268460 28301302 28557808 28571334 28586446 28650834 28673162 28755186 28869440 28891074 28892870 28993696 29173516 29242790 29252466 29420948 29615708 29652588 29667260 29712396 29721802 29785538 29815500 29921086 30010294 30021856 30207658 30239030 30404404 30434172 30802884 30974216 30986868 31036206 31239744 31445750 31447144 31511860 31697302 31798656 31935886 32358434 32396118 32405610 32422084 32463028 32891372 32910540 32915544 33034040 33112556 33381416 33424304 33430490 33573070 33573138 33644288 33966024 34410222 34468032 34554354 34639564 34674870 34822194 34875654 34890750 34934836 35033874 35242026 35252438 35417398 35429674 35499568 35538016 35550710 35593678 35694480 35701238 35791356 35967498 36170182 36188718 36258288 36367446 36429026 36465632 36554880 36591234 36619214 36955096 37012138 37014478 37069104 37080844 37222692 37289184 37477478 37525066 37539082 37731398 37723960 37919898 37955742 38166298 38204376 38296030 38398404 38437674 38532442 38572858 38672504 38732164 38794556 38796892 38808992 38876358 38884144 38914702 39109462 39142864 39163776 39280014 39507650 39563960 39615996 39646302 39647020 39772158 39801432 39884560 40134364 40197348 40232118 40257652 40313088 40381188 40604624 40624084 40655430 40697230 40894766 40899438 40951164 40958948 41022582 41015312 41097904 41373534 41376648 41545108 41577848 41585720 41770314 41980792 42026370 42155204 42159980 42204108 42214528 42379292 42463906 42581378 42584798 42648386 42724662 42777640 43083602 43127998 43406228 43613034 43617780 43796074 43845888 43953704 44001880 44220114 44224774 44262564 44273124 44353554 44358274 44371796 44435560 44477904 44543696 44605360 44613578 44755938 44818970 44935222 45030014 45063980 45090978 45119780 45143836 45376298 45629164 45637798 45659574 45698978 45839458 45863930 46022608 46056952 46170810 46582454 46698964 46960218 46983936 47378690 47472846 47595950 47569014 47651824 47946238 47984028 48066320 48096646 48135770 48149268 48157002 48062530 48239150 48331236 48603326 48677646 48769710 48845872 49159028 49298736 49303742 49496924 49523650 49527560 49564282 49578898 49651148 49652988 49655768 49704390 49922164 50123936 50221936 50587866 51031756 51198384 51410204 51492082 51501460 51616728 51728384 51906054 51910848 52075406 52224456 52256606 52294700 52331768 52545018 52773748 52874414 52927856 53007214 53022198 53250488 53513474 53523364 53579878 53738372 53819034 53841266 54032224 54044372 54049292 54070422 54232280 54269880 54609780 54859632 55144710 55175134 55433918 55491168 55742096 55879658 55904786 56226958 56247626 56568622 56738172 56838966 56841438 56991358 57203908 57317268 57361710 57390028 57565718 57591252 57743714 57759468 57837322 57833524 57978144 58228590 58306260 58430022 58446698 58641604 58796050 58836382 58896930 59213912 59241586 59473128 59581078 59587840 59850740 59858148 59909644 60143970 60155332 60197028 60327268 60395700 60672378 60693660 60693544 60737802 60781272 60838920 60852976 61123304 61250164 61281396 61374756 61377584 61388912 61445596 61586622 61608268 61605660 61696642 61715470 61722492 61777432 61862814 61961696 61975666 61978760 62032036 62094976 62105082 62137258 62318154 62327894 62422592 62537488 62647522 62751960 63044270 63345338 63777050 63810168 63806314 63832458 63874536 63930486 63972944 64162084 64353012 64365734 64714688 64741068 64713412 64760412 64804044 64855922 64867956 64898128 64985968 65054868 65068286 65089562 65093132 64714688 65266240 65320658 65344212 65387276 64714688 65514106 65520628 65529328 65772334 65783514 66178446 66193158 66353184 66489992 66581228 66619406 66702198 66732020 66794266 66797836 66880828 66994438 67131166 67543536 67647742 67804828 67799868 67840636 67889194 68002908 68207494 68274864 68436968 69190662 69204292 69187606 69500606 69541996 69789832 69858944 69945900 69043610 70122604 68962894 69756930 70246422 70272906 69753964 70440684 70464022 70495740 70048258 70526044 70730318 70604480 70501724 71049528 71072080 71266866 71270310 71317522 71396914 71424294 71402554 71717128 71924716 71990306 72039366 72078378 72220632 72018316 72507322 72517714 71846790 72557802 72871570 71566294 73258252 73344746 73490616 73568254 73633862 73605148 73702246 73908134 73849266 74177258 74184902 74175006 74395440 74423074 74462706 74761736 75110388 75144604 75170884 75121068 75572312 75813694 75830238 75874810 75909350 75943868 75998140 75998954 76021108 76163854 76256192 76292748 76303116 76621244 76765734 76830754 76839878 77030532 77151556 77251600 77336548 77456816 77653214 77732740 77799572 77854474 78005582 78056554 78088106 78170154 78204572 78346746 78513342 78592730 78854230 78888570 78908368 78927912 78979192 78995780 79313098 79741450 79997300 80009158 80190300 80454716 80502418 80612174 80654880 80627682 80721324 80885288 80949468 81092448 81248152 81204086 81370822 81419654 81464226 81479200 81510990 81524524 81542662 81643512 81917748 81963086 82021296 82216948 82419040 82456836 82510414 82721056 82797180 83436332 83532916 83551588 83955848 84034616 84100142 84238684 84607726 84657054 84779654 84828582 85231318 85326618 85426480 85509180 85538174 85724774 85810740 85962194 86085882 86197780 86266356 86316726 86357100 86390618 86416078 86560194 86559824 86786930 86852980 86907000 86906874 87404222 87538694 87586782 87602080 87822288 87888966 87888968 88040256 88139808 88169528 88188718 88375556 88457536 88499486 88593558 88705770 88711024 88875842 88907932 88913808 88950444 88973858 89057846 89191710 89534186 90036322 90044424 90098824 90158524 90191700 90216162 90493102 90500380 90537066 90558822 90681404 90853870 90897136 90918816 91042040 91053092 91159406 91325814 91442036 91542430 91657968 91670880 91688986 91729308 91960990 91992926 92248286 92332160 92788434 93026652 93029694 93167764 93195672 93218150 93335534 93343682 93449606 93472028 93495032 93544108 93577266 93583888 93768930 93822920 93970766 94191588 94526242 94533120 94561956 94569926 94719100 94821812 94907042 95031798 95156930 95204390 95318702 95444178 95528838 95714646 95750230 95796272 95948598 95980204	Starting in December 2015, PrimeGrid ran a two-pass search on BOINC using Genefer, finding 822 primes. All b up to 95899542 have been checked as of 27th July 2018.
	Starting in December 2015, PrimeGrid is running a two-pass search on BOINC using Genefer. As of 27th July 2018, the leading edge is b=96203186.

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GFN Prime Search Status: n=16

As of 27th July 2018, there are 424 known primes of the form b^2^16+1 = b^65536+1.

The following values of b give primes:

b	Range status
48594 108368 141146 189590 255694 291726 292550 357868 440846 544118 549868 671600 843832 857678 1024390 1057476 1087540 * 1266062 1361846 1374038 1478036 1483076 1540550	Searched up to b=1.86M by Yves Gallot's GFN Search, using Proth.exe. According to this page, all of the range was reserved but it is unclear if all the reserved tests were completed. 22 primes were reported up to May 2003 PrimeGrid restarted the search in Dec 2011 using PRPNet and Genefer, LLR and PFGW. This effort found 1 previously undiscovered prime (*). A full double-check was carried out on BOINC by PrimeGrid using Genefer in October 2015.
1828502 1874512 1927034 *	2 primes were reported in this range in March 2005 and June 2008, found using Proth.exe. The range has been covered by the PrimeGrid PRPNet search, and has been fully double-checked on BOINC using Genefer, finding 1 previously undiscovered prime (*).
1966374 * 2019300 * 2041898 * 2056292 * 2162068 2177038 2187182	3 primes were reported in this range by Ayeni between July 2008 and April 2009, using Proth.exe. A double-check on BOINC by PrimeGrid using Genefer in November 2015 found 4 previously undiscovered primes (*).
2251082 2313394 2336976 2483590 2484264 2679102 * 2689202 * 2738848 2744940 2779470 2829122 2909834 * 3095674 3422670 3446048 3461954 3462728 3503138 3553248 3785880 3803826 3872228 3877352 3912496 3939670 3966304	This range was checked by PrimeGrid's PRPNet search using Genefer, LLR and PFGW, yielding 23 primes. A single-pass up to b=4205312 was completed on 13 October 2015. A double-check on BOINC by PrimeGrid using Genefer was completed in December 2015. 3 previously undiscovered primes (*) were found.
4280722 4470420 4603702 4615890 4855782 4891596 5143624 5176028 5200658 5222640 5263190 5645768 5350408 5416598 5879074 5905206 5911446 6031270 6068296 6104728 6379668 6490328 6526168 6553414 6628260 6837196 6885798 6902598 6918698 6919394 7107770 7188654 7307674 7373894 7427232 7439308 7464550 7622010 7634800 7832756 7954812 8036146 8099100 8146592 8188038 8326702 8412634 8525558 8596942 8718098 8749120 8844704 9074206 9132408 9214424 9223072 9373148 9392774 9444368 9518248 9584088 9624110 9628238 9841672 9920216 10090890 10221008 10464954 10663638 10755500 10771330 10808098 10957508 11033686 11110588 11168512 11215796 11224312 11292580 11611202 11793760 11804536 11844886 11948010 12084448 12102810 12376146 12508790 12510100 12620940 12660574 12764608 12914686 12941970 13029860 13332130 13398688 13466298 13657452 13830802 13944760 13968798 14050484 14059910 14518950 14705866 14750712 14778298 14807318 14832074 14832496 14914230 14914430 14947856 15005274 15069494 15454262 15471020 15499198 15603948 15800506 15893070 15948188 16034826 16120142 16326986 16787702 16858742 17157558 17265602 17328156 17493552 17594396 17716338 17757426 17629398 * 17655444 * 17684828 * 17770454 17931126 18255116 18364744 18387422 18612352 18682542 18788582 19149988 19165998 19194688 19415886 19432158 19451454 19502212 * 19514276 19810832 19916902 20109598 20317650 20338906 20338564 20368808 20416586 20417546 20495674 20670628 20673706 20794390 20958760 21003082 21123886 21207594 21298612 21352892 21438976 21632926 21697066 21844548 21928344 21946386 21990626 22082900 22191882 22230230 22402670 22602162 22672358 22677562 22684548 22696662 22740816 22738600 22858812 22872882 22877386 23077164 23080390 23138154 23582210 23864352 23947122 24163706 24220066 24293444 24510980 24528070 24722142 24730888 24813140 24859030 25069382 25226438 25281714 25355170 25369696 25815054 25893048 25894728 25939926 25981818 25987186 26477248 26484668 26578974 26886748 26916240 26987486 27243670 27264470 27326204 27372028 27548300 27625562 27639120 27678634 27738902 27768276 28027008 28099080 27441534 28413758 28487278 28580718 28768058 29048042 29097708 29202654 29247740 29340732 29350290 29509260 29501096 29585874 29723118 29863462 30046920 30101988 30216696 30250088 30328508 30376064 30799220 30813412 30877996 30946880 31125356 31154730 31380744 31342854 31448254 31492936 31515202 31613530 31647504 31689074 31812740 31887064 31988978 32056116 32161210 32235030 32370056 32517922 32574488 32675102 32697566 32778852 32987968 33058194 33075870 33112172 33160366 33255290 33388034 33406946 33417368 33468724 33531480 33790428 33910364 33963124 34197950 34327650 34397974 34503816 34575414 34640098 34904540 35255372 35419084 35458620 35534500 35599734 35648406 35753376 36037446 36127768 36187924 36251736 36279762 36362214 36427586 36614838 36633974 36968128 37219594 37284376 37463776 37592308 37732056 37878964 37887878 38040628 38199804 38385824 38472570 38481086 38485606 38542914 38670832 38659632 38770952 38849156 38881766 38951594 39089796 39108392 39162320 39418466 39542162 39641162 39641632 39672694 39809082 39822410 39822830 40348160 40374324 40522376 40547834 40726656 40782880 40858208 40934648 40951894 41023954	Starting in December 2015, PrimeGrid is running a two-pass search on BOINC using Genefer, finding 361 primes. 4 primes (*) were previously reported by independent searchers. As of 27th July 2018, all b up to 41059584 have been checked.
	Starting in December 2015, PrimeGrid is running a two-pass search on BOINC using Genefer. As of 27th July 2018, the leading edge is b=41245342.

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GFN Prime Search Status: n=17

As of 27th July 2018, there are 107 known primes of the form b^2^17+1 = b^131072+1.

The following values of b give primes:

b	Range status
62722 130816 228188 386892 572186 689186 909548 * 1063730 1176694 1361244 1372930	Between 2002 and July 2004, Yves Gallot's GFN Prime Search tested ranges up to b=1.4M using Proth.exe, but left several gaps. As a result, only 6 primes were found in this initial search. Several independent searchers, including David Underbakke continued working in the gaps, and another 4 primes were reported between 2009 and 2013. Between June and October 2015, PrimeGrid completed a full re-check of this range on BOINC using Genefer, finding 1 previous undiscovered prime (*)
1560730 1660830 1717162 1722230 1766192 1955556 2194180 2280466 2639850 3450080 3615210 3814944 4085818 4329134 4893072 4974408 5326454 5400728 5471814 5586416 5734100 5877582 6391936 6403134 6705932 7379442 7832704 7858180 7926326 8150484 8704114 8770526 9240606 9419976 9785844 9907326 10037266 10368632 10453790 10765720 10921162 10962066 10994460 11036888 11195602 11267296 11292782 11778792 11876066 12343130 12357518 12512992	PrimeGrid ran a two-pass search of this range on BOINC using Genefer starting in October 2015, finding 52 primes.
	PrimeGrid is currently running a two-pass search on BOINC using Genefer. As of 27th July 2018, the trailing edge is b=12578982 and the leading edge is b=12634984.
	Between the leading edge of the previous range and b=42658772, no organised testing has been carried out, and no primes are known.
42654182 43163894 43165206 44049878 44085096 44330870 44438760 44919410 45315256 45570624 46077492 46371508 46385310 46413358 46730280 46736070 46776558 47090246 48273828 48370248 48643706 49038514 49090565 49225986 49243622 49331672 49397682 49530004 49817700 50055102 50110436 50217306 50495632 50844724 50963598 51269192 51567684 51570250 51580416 51872628 51954384 52043532 52412612	PrimeGrid is also running a two-pass search on BOINC using Genefer starting from b=42597774 (which would give a million digit prime). As of 27th July 2018, all b up to 52475486 have been checked and 45 primes have been found.
	As of 27th July 2018, the leading edge of this search is 52542792.

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GFN Prime Search Status: n=18

As of 27th July 2018, there are 25 known primes of the form b^2^18+1 = b^262144+1.

The following values of b give primes:

b	Range status
24518 40734 145310 361658	Yves Gallot's GFN Prime Search tested several ranges up to b=589708 using Proth.exe but did not find any primes. In 2008, Stephen Scott reported 1 prime: 24518^262144+1, found using Proth.exe. Starting in 2011, PrimeGrid ran a single-pass search on PRPNet, using Genefer, LLR and PFGW, and found the other 3 primes. A full double-check of this range by PrimeGrid using Genefer on BOINC was completed in August 2015.
525094 676754 773620	This range has been searched by PrimeGrid partly on PRPNet using Genefer, LLR and PFGW and partly on BOINC using Genefer. A total of 3 primes were found A full double-check of this range by PrimeGrid using Genefer on BOINC was completed in August 2015.
1415198 1488256 1615588 1828858 2042774 2514168 2611294 2676404 3060772 3547726 3596074 3673932 3853792 3933508 4246258 4489246 5152128 5205422	PrimeGrid ran a two-pass search of this range on BOINC using Genefer starting in November 2015, finding 18 primes.
	PrimeGrid is currently running a two-pass search on BOINC using Genefer. As of 27th July 2018, the trailing edge is b=5266628 and the leading edge is b=5416030.

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GFN Prime Search Status: n=19

As of 27th July 2018, there are 6 known primes of the form b^2^19+1 = b^524288+1.

The following values of b give primes:

b	Range status
75898 341112 356926 475856 1880370 2061748	Starting in 2011, PrimeGrid ran a single-pass search on PRPNet, using Genefer, LLR and PFGW, and found 1 prime. A full double-check of this range was then carried out by PrimeGrid using Genefer on BOINC. The range was extended with a two-pass search on BOINC using Genefer, finding 5 primes. As of 27th July 2018, all candidates up to b=2231464 have been double-checked.
	A two-pass search on BOINC using Genefer is currently running. As of 27th July 2018, the trailing edge is b=229746 and the leading edge is b=254994.

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GFN Prime Search Status: n=20

As of 27th July 2018, there is 1 known prime of the form b^2^20+1 = b^1048576+1.

The following values of b give primes:

b	Range status
	Between November 2012 and June 2015, PrimeGrid ran a two-pass search on BOINC using Genefer, finding no primes up to b=720000.
919444	Starting in November 2015, PrimeGrid ran a two-pass search on BOINC using Genefer. As of 27th July 2018, all b up to 1000040 have been checked and 1 prime has been found.
	A two-pass search on BOINC using Genefer is currently running. As of 7th July 2018, the leading edge is b=1016444. No primes have been found.

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GFN Prime Search Status: n=21

As of 27th July 2018, there are 0 known primes of the form b^2^21+1 = b^2097152+1.

b	Range status
	Between September and November 2015, PrimeGrid ran a two-pass search on BOINC using Genefer, finding no primes up to b=1350.
	A two-pass search on BOINC using Genefer is currently running. As of 27th July 2018, the leading edge is b=229746.

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GFN Prime Search Status: n=22

As of 27th July 2018, there are 0 known primes of the form b^2^22+1 = b^4194304+1.

b	Range status
	Between February 2012 and November 2015, PrimeGrid ran a two-pass search on BOINC using Genefer, finding no primes up to b=54650.
	A two-pass search on BOINC using Genefer is currently running. As of 27th July 2018, the trailing edge is b=120192 and the leading edge is b=125992.

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