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%I #30 Sep 16 2018 04:37:48
%S 0,1,5,9,11,13,23,135,187,215,233,313,333,493,1459,2753,2813,6411,
%T 31191,38303,41487
%N Numbers k such that k!! + 2^8 is prime.
%C a(22) > 50000. - _Robert Price_, Jan 14 2015
%C a(1)=0 since 0!!=1 and 1 + 2^8 = 257 is prime. - _Robert Price_, Jan 14 2015
%H The OpenPFGW Project, <a href="http://www.primeform.net/openpfgw/">Primality Tester</a>
%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n%212%2B2%5E8&action=Search">PRP Records.</a>
%t lst={}; Do[If[PrimeQ[n!!+2^8], AppendTo[lst, n]], {n, 0, 50000}]; lst
%Y Cf. A006882, A080778 and A076185, A076186, A076188, A076189, A076190, A076193, A076194, 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 a(18) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
%E a(1)=0 prepended and a(19)-a(21) from _Robert Price_, Jan 14 2015