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
Links
- 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
Programs
-
Magma
[n: n in [1..830] | IsPrime(7*2^n+1)]; // Arkadiusz Wesolowski, Feb 24 2017
-
Mathematica
Select[Range[10^3], PrimeQ[7*2^# + 1] &] (* Michael De Vlieger, Feb 25 2017 *)
-
PARI
is(n)=ispseudoprime(7*2^n+1) \\ Charles R Greathouse IV, Feb 20 2017
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