A306647 Numbers k such that 2*k^A006530(k) + 1 is prime.

1, 6, 9, 12, 14, 21, 27, 30, 72, 92, 96, 126, 150, 162, 165, 192, 225, 242, 251, 261, 341, 345, 384, 392, 420, 455, 462, 500, 540, 629, 684, 704, 779, 800, 825, 990, 1350, 1386, 1404, 1482, 1512, 1625, 1725, 1808, 2001, 2028, 2115, 2184, 2322, 2499, 2835

Offset: 1

Author

Jeppe Stig Nielsen, Mar 03 2019

Keywords

• nonn

Comments

All prime members are also in A110932, but the only known example is 251.

Links

• Mathematics Stack Exchange, Are there infinitely many primes of the form 2 m^gpf(m) + 1 when m runs over positive integers?

Crossrefs

Cf. A006530, A110932.

Programs

PARI

print1(1,", ");(gpf(k)=t=factor(k);t[matsize(t)[1],1]);for(k=2,+oo,ispseudoprime(2*k^gpf(k)+1)&&print1(k,", "))