A289855 Primes of the form k!2 - 128, where k!2 is the double factorial number (A006882).

10267, 135007, 13749310447, 1192568192774434123539907640497, 29215606371473169285018060091249259296747, 1009847364737869270905302433221592504062302663202724609247, 34720596058582394465875230149026168047833371128291024141249287753332469144201839599609247

Offset: 1

Author

Robert Price, Jul 13 2017

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..10
• Henri and Renaud Lifchitz, PRP Records.Search for n!2-128.
• Joe McLean, Interesting Sources of Probable Primes.
• OpenPFGW Project, Primality Tester.

Crossrefs

Cf. A006882, A257864.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 2] - 128, {i, 8, 100}], PrimeQ[#]&]
Select[Range[8,120]!!-128,PrimeQ] (* Harvey P. Dale, Dec 01 2018 *)

Formula

a(n) = A006882(A257864(n)) - 128. - Elmo R. Oliveira, Apr 14 2025