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A076185
Numbers n such that n!! + 2 is prime.
18
0, 1, 3, 5, 7, 9, 21, 23, 27, 57, 75, 103, 169, 219, 245, 461, 695, 1169, 3597, 3637, 7495, 27743, 28799, 32501
OFFSET
1,3
COMMENTS
a(25) > 50000. - Robert Price, Jan 18 2015
a(1)=0 since 0!!=1 and 1+2 = 3 is prime. - Robert Price, Jan 18 2015
LINKS
C. K. Caldwell, The Prime Glossary, Multifactorial prime
C. Caldwell and H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), Table 21 F, p. 75
The OpenPFGW Project, Primality Tester
MATHEMATICA
lst={}; Do[If[PrimeQ[n!!+2], AppendTo[lst, n]], {n, 0, 13^3}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 08 2008 *)
Select[Range[0, 33000], PrimeQ[#!!+2]&] (* Harvey P. Dale, Jul 28 2017 *)
CROSSREFS
Cf. A006882, A080778 and A076186, A076188, A076189, A076190, A076193, A076194, A076195, A076196, A076197 for other values of s in n!! + 2^s.
Sequence in context: A003219 A030142 A179085 * A101813 A134719 A373509
KEYWORD
nonn,more
AUTHOR
Zak Seidov, Nov 02 2002
EXTENSIONS
Edited and extended (n<4096) by Hugo Pfoertner, Jun 19 2003
One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Dec 30 2007
a(22) - a(23) from Robert Price, Oct 17 2012
a(24) from Robert Price, Jan 18 2015
STATUS
approved