

A032502


Numbers k such that 251*2^k+1 is prime.


0



1, 11, 13, 17, 35, 77, 155, 325, 4097, 5471, 7151, 7561, 9211, 13535, 14627, 18361, 21815, 41945, 68255, 105947, 119915, 358777, 748745, 843367, 1171193, 2730917
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OFFSET

1,2


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^n1 (or k*2^n+1) is prime


MATHEMATICA

Select[Range[1000], PrimeQ[251*2^# + 1] & ] (* Robert Price, Dec 20 2018 *)


PROG

(PARI) is(n)=ispseudoprime(251*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Sequence in context: A090236 A240623 A240624 * A209871 A347702 A167794
Adjacent sequences: A032499 A032500 A032501 * A032503 A032504 A032505


KEYWORD

nonn,hard,more


AUTHOR

N. J. A. Sloane.


EXTENSIONS

a(21)a(25) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 20 2018
a(26) from Jeppe Stig Nielsen, Feb 25 2020


STATUS

approved



