A076195 Numbers k such that k!! + 2^8 is prime.

0, 1, 5, 9, 11, 13, 23, 135, 187, 215, 233, 313, 333, 493, 1459, 2753, 2813, 6411, 31191, 38303, 41487

Offset

1,3

Comments

a(22) > 50000. - Robert Price, Jan 14 2015

a(1)=0 since 0!!=1 and 1 + 2^8 = 257 is prime. - Robert Price, Jan 14 2015

Links

Table of n, a(n) for n=1..21.

The OpenPFGW Project, Primality Tester

Henri & Renaud Lifchitz, PRP Records.

Mathematica

lst={}; Do[If[PrimeQ[n!!+2^8], AppendTo[lst, n]], {n, 0, 50000}]; lst

Crossrefs

Cf. A006882, A080778 and A076185, A076186, A076188, A076189, A076190, A076193, A076194, A076196, A076197 for other values of s in n!! + 2^s.

Sequence in context: A287521 A287529 A179383 * A191924 A128310 A314586

Adjacent sequences: A076192 A076193 A076194 * A076196 A076197 A076198

Keyword

nonn,more

Author

Zak Seidov, Nov 02 2002

Extensions

Edited and extended (n < 4096) by Hugo Pfoertner, Jun 19 2003

a(18) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

a(1)=0 prepended and a(19)-a(21) from Robert Price, Jan 14 2015

Status

approved