The sixth challenge of the 2021 Series will be a 10-day challenge leading up to a relatively rare astronomical event called a blue moon. The challenge will be offered on the PSP-LLR application, beginning 12 August 20:00 UTC and ending 22 August 20:00 UTC.
To participate in the Challenge, please select only the Prime Sierpinski Problem LLR (PSP) project in your PrimeGrid preferences section.
For more info, check out the forum thread for this challenge: https://www.primegrid.com/forum_thread.php?id=9720&nowrap=true#151032
Best of luck!