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A289686
Numbers k such that k!6 - 8 is prime, where k!6 is the sextuple factorial number (A085158).
1
9, 11, 13, 15, 19, 27, 35, 39, 45, 51, 83, 99, 105, 111, 121, 123, 127, 133, 175, 177, 213, 263, 277, 285, 339, 347, 543, 681, 743, 1069, 1965, 2379, 2613, 2629, 2911, 3767, 3879, 4789, 5493, 5819, 11559, 14555, 17831, 19705, 24867, 37535, 85089
OFFSET
1,1
COMMENTS
Corresponding primes are: 19, 47, 83, 397, 1721, 229627, 21827567, ...
a(48) > 10^5.
Terms > 99 correspond to probable primes.
EXAMPLE
19!6 - 8 = 19*13*7 - 8 = 1721 is prime, so 19 is in the sequence.
MATHEMATICA
MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
Select[Range[8, 50000], PrimeQ[MultiFactorial[#, 6] - 8] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Price, Jul 09 2017
EXTENSIONS
a(47) from Robert Price, Aug 03 2018
STATUS
approved