A261145 - OEIS

A261145

Numbers n such that n!3 + 3^10 is prime, where n!3 = n!!! is a triple factorial number (A007661).

2, 4, 7, 11, 25, 38, 47, 94, 95, 155, 275, 277, 292, 299, 395, 409, 614, 1409, 1963, 3422, 5243, 5884, 5971, 8527, 10882, 13223, 16406, 20851, 28886

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OFFSET

1,1

COMMENTS

Corresponding primes are: 59051, 59053, 59077, 59929, 608667049, 3091650738235049, 262134882788466747049, ...

a(30) > 50000.

Terms > 47 correspond to probable primes.

LINKS

OpenPFGW Project, Primality Tester

EXAMPLE

11!3 + 3^10 = 11*8*5*2 + 59049 = 59929 is prime, so 11 is in the sequence.

MATHEMATICA

MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]];

Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 3] + 3^10] &]

PROG

(PARI) for(n=1, 1e3, if(ispseudoprime(prod(i=0, floor((n-1)/3), n-3*i) + 3^10), print1(n, ", "))) \\ Altug Alkan, Nov 18 2015

CROSSREFS

KEYWORD

nonn,more

AUTHOR

Robert Price, Nov 18 2015

STATUS

approved