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

279, 415, 711, 115807, 241071

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• hard

Links

• 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

Programs

PARI

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

Extensions

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