A322958 Numbers k such that 331*2^k+1 is prime.

4, 8, 12, 20, 28, 36, 120, 184, 200, 756, 788, 1304, 6412, 7848, 12944, 40116, 45056, 67520, 129172, 204592, 225568, 615116, 803668, 1646668, 2917844

Offset: 1

Author

Robert Price, Dec 31 2018

Keywords

• nonn
• more
• hard

Links

• Ray Ballinger, Proth Search Page
• Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for 300 < k < 600
• 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

Crossrefs

Cf. A002255, A050527.

Programs

Maple

select(n->isprime(331*2^n+1),[$1..1000]); # Muniru A Asiru, Dec 31 2018

Mathematica

Select[Range[1000], PrimeQ[331*2^# + 1] &] (* Robert Price, Dec 31 2018 *)

Extensions

a(25) from Jeppe Stig Nielsen, Dec 20 2024