From the 6k mini-drive:

321*2^628734-1 is prime

861*2^645393-1 is a confirmed prime

321*2^650818-1 is prime

849*2^646968-1 is prime

315*2^659232-1 is new prime!

PS: 6 k's, 4 primes from only 2 k's: 315 and 321!

805*2^647277-1 is prime

921*2^647991-1 is prime

321*2^666797-1 is prime

Only k=315 and 321 seem to be able to score from the 6k drive. That's 3 for k=321 and 2 for k=315.


Gary

829*2^649149-1 is prime

383*2^608340-1 is prime

321*2^682493-1 is prime

The trend continues on the 6k drive: For k=315/321/327/333/339/345, that's 4 primes for k=321, 2 primes for k=315, and none for the others.