

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
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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

Table of n, a(n) for n=1..35.
OpenPFGW Project, Primality Tester
Henri & Renaud Lifchitz, PRP Records. Search for n!33


EXAMPLE

11!33 = 11*8*5*23 = 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



