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A242994
Numbers n such that n!3 - 3 is prime, where n!3 = n!!! is a triple factorial number (A007661).
43
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
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
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
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