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%I #40 Nov 08 2017 07:44:12
%S 0,1,3,5,7,11,17,29,39,43,73,93,315,549,2059,5543,6937,22819,34523
%N Numbers n such that n!! + 2^2 is prime.
%C a(20) > 50000. - _Robert Price_, Feb 05 2015
%C Since 0!! is defined to be unity (A006882), 0!! + 2^2 = 5, which is prime. - _Robert Price_, Mar 22 2015
%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n!2%2B4&action=Search">PRP Records. Search for n!2+4.</a>
%H Joe McLean, <a href="http://web.archive.org/web/20091027034731/http://uk.geocities.com/nassarawa%40btinternet.com/probprim2.htm">Interesting Sources of Probable Primes</a>
%H The OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%t Select[Range[0, 1000], PrimeQ[#!! + 4] &] (* _Robert Price_, Mar 22 2015 *)
%Y Cf. A006882, A080778 and A076185, A076188, A076189, A076190, A076193, A076194, A076195, A076196, A076197 for other values of s in n!! + 2^s.
%K nonn,more
%O 1,3
%A _Zak Seidov_, Nov 02 2002
%E Edited and extended (n<4096) by _Hugo Pfoertner_, Jun 19 2003
%E 6937 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
%E Corrected by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
%E a(18) = 22819 from _Robert Price_, Oct 04 2012
%E a(19) = 34523 from _Robert Price_, Feb 05 2015
%E a(1)=0 prepended by _Robert Price_, Mar 22 2015
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