A032474 Numbers k such that 195*2^k+1 is prime.

4, 8, 13, 14, 20, 31, 38, 70, 80, 86, 110, 125, 140, 170, 179, 230, 338, 365, 374, 517, 860, 944, 1045, 1270, 1861, 3623, 4414, 10448, 27766, 30836, 34666, 39826, 55763, 59260, 70228, 71590, 76618, 130388, 189499, 196303, 202307, 239773, 240110, 265954, 422195

Offset

1,1

Links

Jeppe Stig Nielsen, Table of n, a(n) for n = 1..56

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

Maple

select(k->isprime(195*2^k+1), [$0..1000]); # Muniru A Asiru, Dec 18 2018

Mathematica

Select[Range[1000], PrimeQ[195*2^# + 1] & ] (* Robert Price, Dec 18 2018 *)

Prog

(PARI) is(n)=ispseudoprime(195*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A058759 A237519 A311665 * A311666 A222304 A311667

Adjacent sequences: A032471 A032472 A032473 * A032475 A032476 A032477

Keyword

nonn,hard

Author

N. J. A. Sloane

Extensions

a(38)-a(52) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 18 2018

Moved terms from Data section to b-file, and appended more terms to b-file, by Jeppe Stig Nielsen, Jan 18 2020

Status

approved