login
A287914
Numbers k such that k!6 + 4 is prime, where k!6 is the sextuple factorial number (A085158 ).
1
1, 3, 7, 9, 11, 15, 19, 27, 35, 59, 71, 75, 95, 109, 153, 155, 169, 189, 277, 355, 383, 405, 455, 625, 843, 853, 879, 1389, 1423, 1515, 1871, 2059, 2677, 3095, 4473, 5691, 5927, 8149, 10789, 12171, 14683, 26383, 34227, 40945
OFFSET
1,2
COMMENTS
Corresponding primes are: 5, 7, 11, 31, 59, 409, 1733, 229639, 21827579, ...
a(45) > 50000.
Terms > 35 correspond to probable primes.
EXAMPLE
11!6 + 4 = 11*5 + 4 = 59 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] + 4] &]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Jun 02 2017
STATUS
approved