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A289686 Numbers k such that k!6 - 8 is prime, where k!6 is the sextuple factorial number (A085158).

%I A289686 #15 Nov 29 2018 17:55:32
%S A289686 9,11,13,15,19,27,35,39,45,51,83,99,105,111,121,123,127,133,175,177,
%T A289686 213,263,277,285,339,347,543,681,743,1069,1965,2379,2613,2629,2911,
%U A289686 3767,3879,4789,5493,5819,11559,14555,17831,19705,24867,37535,85089
%N A289686 Numbers k such that k!6 - 8 is prime, where k!6 is the sextuple factorial number (A085158).
%C A289686 Corresponding primes are: 19, 47, 83, 397, 1721, 229627, 21827567, ...
%C A289686 a(48) > 10^5.
%C A289686 Terms > 99 correspond to probable primes.
%H A289686 Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n!6-8&amp;action=Search">PRP Records. Search for n!6-8.</a>
%H A289686 Joe McLean, <a href="http://web.archive.org/web/20091027034731/http://uk.geocities.com/nassarawa%40btinternet.com/probprim2.htm">Interesting Sources of Probable Primes</a>
%H A289686 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%e A289686 19!6 - 8 = 19*13*7 - 8 = 1721 is prime, so 19 is in the sequence.
%t A289686 MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
%t A289686 Select[Range[8, 50000], PrimeQ[MultiFactorial[#, 6] - 8] &]
%Y A289686 Cf. A007661, A037082, A084438, A123910, A242994.
%K A289686 nonn
%O A289686 1,1
%A A289686 _Robert Price_, Jul 09 2017
%E A289686 a(47) from _Robert Price_, Aug 03 2018