Michael Goetz Volunteer moderator Project administrator Project scientist Send message Joined: 21 Jan 10 Posts: 12683 ID: 53948 Credit: 184,880,120 RAC: 197,398
Congratulations to DeleteNull for finding the 2.6 million digit mega-prime 273809*2^8932416-1 and eliminating k=273809 from the Riesel Problem! 49 k's remain.
This is PrimeGrid's 60th mega prime of 2017, our 195th mega prime overall, and the 15th k eliminated by PrimeGrid from The Riesel Problem. This is also DeleteNull's second mega-prime, as well as the second k he's eliminated from one of the our conjecture projects. (Click here for the full list of DeleteNull's prime discoveries at PrimeGrid.)
____________ Please do not PM me with support questions. Ask on the forums instead. Thank you!
But it depends on the perspective. If you write the candidate as:
N = k·2^n - 1
then you are right, we see a minus one.
But if you express instead, in terms of N, the number that is smooth to factor, that is N + 1, so for example in the help for PFGW, you can see:
-t currently performs a deterministic test. By default this is an N-1
test, but N+1 testing may be selected with '-tp'. N-1 or N+1 is
factored, and Pocklington's or Morrison's Theorem is applied. If 33%
size of N prime factors are available, the Brillhart-Lehmer-Selfridge
test is applied for conclusive proof of primality. If less than 33%
is factored, this test provides 'F-strong' probable primality with
respect to the factored part F.