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 A242994 Numbers n such that n!3 - 3 is prime, where n!3 = n!!! is a triple factorial number (A007661). 42
 5, 10, 11, 13, 16, 22, 28, 71, 74, 94, 119, 121, 134, 157, 200, 262, 286, 484, 1039, 1045, 1190, 1595, 1679, 1772, 1789, 2410, 2920, 5039, 7919, 10462, 11846, 23293, 26705, 30781, 43694 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Large terms correspond to probable primes. - Jens Kruse Andersen, Aug 19 2014 a(36) > 50000. - Robert Price, Oct 12 2014 LINKS OpenPFGW Project, Primality Tester Henri & Renaud Lifchitz, PRP Records. Search for n!3-3 EXAMPLE 11!3-3 = 11*8*5*2-3 = 877 is prime, so 11 is in the sequence. - Jens Kruse Andersen, Aug 19 2014 MATHEMATICA MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]]; lst={}; Do[If[PrimeQ[MultiFactorial[n, 3] - 3], AppendTo[lst, n]], {n, 100}]; lst CROSSREFS Cf. A007661, A037082, A084438, A243078. Sequence in context: A134002 A028760 A028807 * A070791 A173901 A016084 Adjacent sequences:  A242991 A242992 A242993 * A242995 A242996 A242997 KEYWORD nonn,more AUTHOR Robert Price, Aug 17 2014 EXTENSIONS Links and crossrefs fixed by Jens Kruse Andersen, Aug 19 2014 a(35) from Robert Price, Oct 12 2014 STATUS approved

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Last modified November 30 18:31 EST 2021. Contains 349424 sequences. (Running on oeis4.)