A032353 Numbers k such that 7*2^k+1 is prime.

2, 4, 6, 14, 20, 26, 50, 52, 92, 120, 174, 180, 190, 290, 320, 390, 432, 616, 830, 1804, 2256, 6614, 13496, 15494, 16696, 22386, 54486, 88066, 95330, 207084, 283034, 561816, 804534, 811230, 1491852, 2139912, 2167800, 2915954, 3015762, 3511774, 5775996

Offset

1,1

Links

Table of n, a(n) for n=1..41.

Ray Ballinger, Proth Search Page

Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300

Y. Gallot, Proth.exe: Windows Program for Finding Large Primes

Wilfrid Keller, List of primes k.2^n - 1 for k < 300

Eric Weisstein's World of Mathematics, Proth Prime

Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime

Mathematica

Select[Range[10^3], PrimeQ[7*2^# + 1] &] (* Michael De Vlieger, Feb 25 2017 *)

Prog

(PARI) is(n)=ispseudoprime(7*2^n+1) \\ Charles R Greathouse IV, Feb 20 2017
(Magma) [n: n in [1..830] | IsPrime(7*2^n+1)]; // Arkadiusz Wesolowski, Feb 24 2017

Crossrefs

Cf. A002255, A050527.

Sequence in context: A277909 A064409 A225078 * A062112 A226302 A337499

Adjacent sequences: A032350 A032351 A032352 * A032354 A032355 A032356

Keyword

nonn,hard

Author

James R. Buddenhagen

Extensions

Added more terms (from http://web.archive.org/web/20161028080239/http://www.prothsearch.net/riesel.html), Joerg Arndt, Apr 07 2013

a(41) from Jeppe Stig Nielsen, Jul 25 2019

Status

approved