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

1,2

Comments

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

Links

Table of n, a(n) for n=1..51.

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

Prog

(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, ", "))

Crossrefs

Cf. A006530, A110932.

Sequence in context: A267918 A330703 A262828 * A189728 A214777 A239310

Adjacent sequences: A306644 A306645 A306646 * A306648 A306649 A306650

Keyword

nonn

Author

Jeppe Stig Nielsen, Mar 03 2019

Status

approved