A032479 Numbers k such that 205*2^k+1 is prime.

2, 6, 26, 30, 40, 86, 126, 130, 150, 240, 786, 1146, 2974, 5162, 5750, 14256, 30894, 35622, 42714, 89290, 93456, 111926, 112162, 760450, 1355814, 1358016

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[205*2^# + 1] & ] (* Robert Price, Dec 19 2018 *)

Prog

(PARI) is(n)=ispseudoprime(205*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A109286 A009466 A348067 * A029988 A050573 A337573

Adjacent sequences: A032476 A032477 A032478 * A032480 A032481 A032482

Keyword

nonn,hard,more

Author

N. J. A. Sloane.

Extensions

a(20)-a(26) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 19 2018

Status

approved