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%I A082671 #18 Sep 08 2022 08:45:10
%S A082671 3,4,5,6,9,31,41,373,589,812,989,1115,1488,1864,1918,4412,4686,5821,
%T A082671 13830
%N A082671 Numbers n such that (n!-2)/2 is a prime.
%e A082671 (4!-2)/2 = 11 is a prime.
%t A082671 Select[Range[0, 14000], PrimeQ[(#! - 2) / 2] &] (* _Vincenzo Librandi_, Feb 18 2015 *)
%o A082671 (PARI) xfactpk(n,k=2) = { for(x=2,n, y = (x!-k)/k; if(isprime(y),print1(x", ")) ) }
%o A082671 (Magma) [n: n in [1..600]| IsPrime((Factorial(n)-2) div 2)]; // _Vincenzo Librandi_, Feb 18 2015
%Y A082671 Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199, A139200, A139201, A139202, A139203, A139204, A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071
%K A082671 hard,more,nonn
%O A082671 1,1
%A A082671 _Cino Hilliard_, May 18 2003
%E A082671 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
%E A082671 Edited by _T. D. Noe_, Oct 30 2008

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