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A261145 Numbers n such that n!3 + 3^10 is prime, where n!3 = n!!! is a triple factorial number (A007661). 6
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

a(30) > 50000.

Terms > 47 correspond to probable primes.

LINKS

Table of n, a(n) for n=1..29.

Henri & Renaud Lifchitz, PRP Records. Search for n!3+59049.

Joe McLean, Interesting Sources of Probable Primes

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

Cf. A007661, A037082, A084438, A123910, A242994.

Sequence in context: A071250 A084992 A304040 * A277339 A153555 A259588

Adjacent sequences:  A261142 A261143 A261144 * A261146 A261147 A261148

KEYWORD

nonn,more

AUTHOR

Robert Price, Nov 18 2015

STATUS

approved

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Last modified October 22 11:49 EDT 2021. Contains 348168 sequences. (Running on oeis4.)