A076195 -id:A076195 - cp's OEIS frontend

A259045 Numbers n such that n!! - 2^6 is prime.

7, 9, 11, 17, 21, 27, 29, 39, 43, 45, 67, 145, 173, 613, 833, 1449, 1703, 1719, 2673, 19661, 36095, 37837, 37845

Offset: 1

Robert Price, Jun 17 2015

a(24) > 50000.

C. K. Caldwell, The Prime Glossary, multifactorial prime
Joe McLean, Interesting Sources of Probable Primes

Cf. A007749, A094144, A123910, A257864 (other forms of n!!-2^k)

Cf. A080778, A076185, A076186, A076188, A076189, A076190, A076193, A076194, A076195, A076196, A076197 (other forms of n!!+2^k)

Select[Range[0, 50000], #!! - 64 > 0 && PrimeQ[#!! - 64] &]
Select[Range[4, 6000], PrimeQ[#!! - 64] &] (* Vincenzo Librandi, Jun 18 2015 *)

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

Original entry on oeis.org

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

Offset: 1

Robert Price, Jun 08 2017

nonn

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

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

Cf. A076195.

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 *)

cp's OEIS Frontend

A259045 Numbers n such that n!! - 2^6 is prime.

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