A032499 Numbers k such that 245*2^k+1 is prime.

1, 5, 9, 25, 69, 73, 99, 153, 163, 223, 273, 279, 331, 439, 445, 595, 601, 1189, 2311, 3523, 3773, 5369, 6349, 8743, 14083, 25225, 25371, 37773, 60615, 123471, 136993, 225185, 242925, 251025, 275419, 354079, 441021, 458995, 930031, 2748663

Offset

1,2

Links

Table of n, a(n) for n=1..40.

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[245*2^# + 1] & ] (* Robert Price, Dec 20 2018 *)

Prog

(PARI) is(n)=ispseudoprime(245*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A301960 A050359 A062812 * A112084 A038251 A034498

Adjacent sequences: A032496 A032497 A032498 * A032500 A032501 A032502

Keyword

nonn,hard,more

Author

N. J. A. Sloane.

Extensions

a(32)-a(39) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 20 2018

a(40) from Jeppe Stig Nielsen, Feb 25 2020

Status

approved