A032505 Numbers n such that 257*2^n+1 is prime.

279, 415, 711, 115807, 241071

Offset

1,1

Links

Table of n, a(n) for n=1..5.

Ray Ballinger, Proth Search Page

Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300

Wilfrid Keller, List of primes k.2^n - 1 for k < 300

Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime

Prog

(PARI) is(n)=ispseudoprime(257*2^n+1) \\ Charles R Greathouse IV, Jun 07 2017

Crossrefs

Sequence in context: A251624 A062384 A053345 * A252855 A331265 A038656

Adjacent sequences: A032502 A032503 A032504 * A032506 A032507 A032508

Keyword

nonn,hard

Author

N. J. A. Sloane.

Extensions

One more term (from the Ballinger-Keller web page) from M. F. Hasler, Apr 18 2007

Status

approved