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A247865
Numbers n such that n!3 + 3^2 is prime.
1
2, 4, 5, 7, 8, 14, 17, 19, 22, 23, 26, 34, 46, 59, 70, 86, 100, 101, 118, 148, 151, 160, 200, 281, 317, 343, 682, 842, 853, 871, 1244, 1988, 2170, 2389, 2728, 3049, 3661, 4678, 9169, 12767, 16072, 19808, 20710, 33142, 33442
OFFSET
1,1
COMMENTS
Large terms correspond to probable primes.
a(46) > 50000.
LINKS
Henri & Renaud Lifchitz, PRP Records. Search for n!3+9
OpenPFGW Project, Primality Tester
Eric Weisstein's World of Mathematics, Multifactorial.
EXAMPLE
8!3+9 = 8*5*2+9= 89 is prime, so 8 is in the sequence.
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] + 9], AppendTo[lst, n]], {n, 100}]; lst
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Sep 25 2014
STATUS
approved