A032507 Numbers k such that 261*2^k+1 is prime.

1, 3, 4, 5, 7, 9, 11, 27, 29, 37, 57, 59, 67, 71, 73, 101, 117, 155, 157, 160, 193, 195, 208, 273, 303, 328, 357, 433, 443, 444, 479, 587, 1095, 1101, 1149, 1291, 1319, 1580, 2065, 2137, 2225, 2796, 3025, 3195, 4396, 6309, 6396, 6933, 6955, 8271, 8691, 10688

Offset

1,2

Links

Jeppe Stig Nielsen, Table of n, a(n) for n = 1..94 (terms n = 1..91 from Robert Price)

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[261*2^# + 1] & ] (* Robert Price, Dec 20 2018 *)

Prog

(PARI) is(n)=ispseudoprime(261*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A049646 A033556 A219044 * A325462 A063950 A010420

Adjacent sequences: A032504 A032505 A032506 * A032508 A032509 A032510

Keyword

nonn,hard

Author

N. J. A. Sloane.

Extensions

a(52)-a(91) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 20 2018

Status

approved