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A247866
Numbers k such that k!3 + 3^4 is prime.
1
2, 7, 14, 16, 22, 23, 26, 40, 43, 47, 58, 62, 70, 107, 265, 292, 439, 874, 982, 1063, 1150, 2506, 3578, 3775, 7679, 10024, 42625, 46714
OFFSET
1,1
COMMENTS
Large terms correspond to probable primes.
a(29) > 50000.
LINKS
Henri & Renaud Lifchitz, PRP Records. Search for n!3+81
OpenPFGW Project, Primality Tester
Eric Weisstein's World of Mathematics, Multifactorial.
EXAMPLE
7!3 + 81 = 7*4*1 + 81 = 109 is prime, so 7 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] + 81], AppendTo[lst, n]], {n, 100}]; lst
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Sep 25 2014
STATUS
approved