Prime? Nice try, but no cigar!!

[kriesel]

Originally Posted by GP2

Did you retain the output from the first run? If so, can you post it here as an attachment?

If the Residue column says 0x0000000000000000 for anything but the final result, it's almost certainly bad.

Or the iteration before last, but no earlier than that, for the LL sequence done correctly. Iteration # p-3 for Mp can have that res64. See "penultimate Lucas Lehmer step" thread, particularly https://www.mersenneforum.org/showpo...43&postcount=7