

A076186


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


11



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

1,3


COMMENTS

a(20) > 50,000.  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

Table of n, a(n) for n=1..19.
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

Cf. A006882, A080778 and A076185, A076188, A076189, A076190, A076193, A076194, A076195, A076196, A076197 for other values of s in n!! + 2^s.
Sequence in context: A248714 A091567 A241896 * A092564 A068811 A088083
Adjacent sequences: A076183 A076184 A076185 * A076187 A076188 A076189


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



