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 A202426 Numbers n such that  n!*n!! - 1 is prime. 1
 2, 3, 4, 10, 11, 13, 17, 22, 26, 36, 79, 196 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS No additional terms up to n=1000. - Harvey P. Dale, Oct 29 2016 LINKS EXAMPLE for n = 4, 4!*4!! + 1 = 24*8 - 1 = 191 is prime. MATHEMATICA lst={}; Do[If[PrimeQ[n!*n!!-1], AppendTo[lst, n]], {n, 500}]; lst Select[Range[200], PrimeQ[#!#!!-1]&] (* Harvey P. Dale, Oct 29 2016 *) PROG (MAGMA) a:=func< n | Factorial(n)*(&*[n..2 by -2])-1 >; [ n: n in [0..660] | IsPrime(a(n)) ];  // Bruno Berselli, Dec 19 2011 CROSSREFS Cf. A000142, A006882, A202424 (associated primes). Sequence in context: A080897 A117383 A047455 * A039002 A295393 A120023 Adjacent sequences:  A202423 A202424 A202425 * A202427 A202428 A202429 KEYWORD nonn AUTHOR Michel Lagneau, Dec 19 2011 STATUS approved

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Last modified February 27 12:22 EST 2020. Contains 332306 sequences. (Running on oeis4.)