A076189 Numbers k such that k!! + 2^4 is prime.

0, 1, 3, 5, 13, 17, 25, 27, 39, 45, 47, 53, 177, 217, 401, 637, 729, 787, 843, 3407, 8835, 10283, 14061, 21951

Offset: 1

Author

Zak Seidov, Nov 02 2002

Keywords

• nonn
• more

Comments

a(25) > 50000. - Robert Price, Jan 19 2015

a(1)=0 since 0!!=1 and 1 + 2^4 = 17 is prime. - Robert Price, Jan 19 2015

Links

• The OpenPFGW Project, Primality Tester
• Henri & Renaud Lifchitz, PRP Records.

Crossrefs

Cf. A006882, A080778 and A076185, A076186, A076188, A076190, A076193, A076194, A076195, A076196, A076197 for other values of s in n!! + 2^s.

Programs

Maple

select(t -> isprime(doublefactorial(t)+16), [$0..1000]); # Robert Israel, Jan 19 2015

Mathematica

lst={}; Do[If[PrimeQ[n!!+2^4], AppendTo[lst, n]], {n, 0, 50000}]; lst

Extensions

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

8835 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

a(22)-a(24) from Robert Price, Jan 01 2013

a(1)=0 prepended by Robert Price, Jan 19 2015