

A287956


Numbers k such that k!6 + 6 is prime, where k!6 is the sextuple factorial number (A085158 ).


1



1, 5, 7, 11, 13, 17, 37, 43, 55, 107, 139, 149, 157, 211, 223, 343, 373, 409, 523, 12049, 16457, 17143, 17543, 18391, 25829, 25945, 31307, 34601, 41687
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OFFSET

1,2


COMMENTS

Corresponding primes are: 7, 11, 13, 61, 97, 941, 49579081, 2131900231, 5745471106381, ...
a(43) > 50000.
Terms > 35 correspond to probable primes.


LINKS

Table of n, a(n) for n=1..29.
Henri & Renaud Lifchitz, PRP Records. Search for n!6+6.
Joe McLean, Interesting Sources of Probable Primes
OpenPFGW Project, Primality Tester


EXAMPLE

11!6 + 6 = 11*5 + 6 = 61 is prime, so 11 is in the sequence.


MATHEMATICA

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n  k, k]];
Select[Range[0, 50000], PrimeQ[MultiFactorial[#, 6] + 6] &]


CROSSREFS

Cf. A007661, A037082, A084438, A123910, A242994.
Sequence in context: A230217 A317250 A007529 * A266266 A246463 A314297
Adjacent sequences: A287953 A287954 A287955 * A287957 A287958 A287959


KEYWORD

nonn,more


AUTHOR

Robert Price, Jun 03 2017


STATUS

approved



