A076186 Numbers n such that n!! + 2^2 is prime.

0, 1, 3, 5, 7, 11, 17, 29, 39, 43, 73, 93, 315, 549, 2059, 5543, 6937, 22819, 34523

Offset: 1

Author

Zak Seidov, Nov 02 2002

Keywords

• nonn
• more

Comments

a(20) > 50000. - Robert Price, Feb 05 2015

Since 0!! is defined to be unity (A006882), 0!! + 2^2 = 5, which is prime. - Robert Price, Mar 22 2015

Links

• Henri & Renaud Lifchitz, PRP Records. Search for n!2+4.
• Joe McLean, Interesting Sources of Probable Primes
• The OpenPFGW Project, Primality Tester

Crossrefs

Cf. A006882, A080778 and A076185, A076188, A076189, A076190, A076193, A076194, A076195, A076196, A076197 for other values of s in n!! + 2^s.

Programs

Mathematica

Select[Range[0, 1000], PrimeQ[#!! + 4] &] (* Robert Price, Mar 22 2015 *)

Extensions

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

6937 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

Corrected by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

a(18) = 22819 from Robert Price, Oct 04 2012

a(19) = 34523 from Robert Price, Feb 05 2015

a(1)=0 prepended by Robert Price, Mar 22 2015