A288411 Primes of the form k!2+256, where k!2 is the double factorial number (A006852).

257, 271, 1201, 10651, 135391, 316234143481, 49988475139107080748861383849035044804037186461213252284425520655249250725695020643146597883951938106998443603515881

Offset: 1

Author

Robert Price, Jun 08 2017

Keywords

• nonn

Comments

The next term has 174 digits. - Harvey P. Dale, Mar 09 2018

Links

• Robert Price, Table of n, a(n) for n = 1..8
• Henri& Renaud Lifchitz, PRP Records.Search for n!2+256.
• Joe McLean, Interesting Sources of Probable Primes
• OpenPFGW Project, Primality Tester

Crossrefs

Cf. A076195.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 2] + 256, {i, 0, 100}], PrimeQ[#]&]
Select[Range[200]!!+256,PrimeQ] (* Harvey P. Dale, Mar 09 2018 *)