A032413 Numbers k such that 127*2^k+1 is prime.

2, 12, 18, 24, 54, 72, 114, 180, 214, 504, 558, 964, 1098, 1420, 2764, 4322, 5582, 10538, 14634, 23970, 61054, 67318, 88958, 96744, 297350, 357840, 376162, 723530, 916980, 925012, 1472718, 1817862, 5391378

Offset: 1

Author

James R. Buddenhagen

Keywords

• nonn
• more

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

Crossrefs

Cf. A032418.

Programs

Mathematica

Select[Range[1000], PrimeQ[127*2^# + 1] & ] (* Robert Price, Dec 17 2018 *)

PARI

is(n)=ispseudoprime(127*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(25)-a(32) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 17 2018

a(33) from Jeppe Stig Nielsen, Dec 23 2024