OFFSET
1,3
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
MATHEMATICA
Select[Range[0, 1000], PrimeQ[#!! + 4] &] (* Robert Price, Mar 22 2015 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Zak Seidov, Nov 02 2002
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
STATUS
approved