A032455 Numbers k such that 157*2^k+1 is prime.

8, 12, 14, 24, 32, 134, 252, 272, 404, 1460, 1776, 8510, 14280, 14396, 17736, 21284, 84056, 147036, 490772, 963590, 1920152, 2407958

Offset

1,1

Links

Table of n, a(n) for n=1..22.

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

Mathematica

Select[Range[1000], PrimeQ[157*2^# + 1] & ] (* Robert Price, Dec 18 2018 *)

Prog

(PARI) is(n)=ispseudoprime(157*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A108979 A107071 A114414 * A342809 A279963 A050275

Adjacent sequences: A032452 A032453 A032454 * A032456 A032457 A032458

Keyword

nonn,hard,more

Author

N. J. A. Sloane.

Extensions

a(17)-a(21) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 18 2018

a(22) from Jeppe Stig Nielsen, Apr 04 2020

Status

approved