A032475 Numbers k such that 197*2^k+1 is prime.

15, 19, 35, 55, 59, 115, 163, 371, 1175, 3047, 5615, 7855, 9155, 16467, 22303, 32879, 66123, 70619, 85607, 117047, 238083, 354335, 1502095, 1568755, 1830255, 2244347

Offset

1,1

Links

Table of n, a(n) for n=1..26.

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[197*2^# + 1] & ] (* Robert Price, Dec 19 2018 *)

Prog

(PARI) is(n)=ispseudoprime(197*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A164564 A211329 A104298 * A169728 A167054 A241680

Adjacent sequences: A032472 A032473 A032474 * A032476 A032477 A032478

Keyword

nonn,hard,more

Author

N. J. A. Sloane.

Extensions

a(20)-a(25) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 19 2018

a(26) from Jeppe Stig Nielsen, Apr 19 2020

Status

approved