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%I #18 Nov 29 2018 16:22:01
%S 8,10,16,22,26,46,52,56,70,74,286,302,308,484,698,1100,1226,1528,2486,
%T 3796,4256,8524,10688,19424,22226,49346,53746,64178,84304
%N Numbers k such that k!6 - 9 is prime, where k!6 is the sextuple factorial number (A085158).
%C Corresponding primes are: 7, 31, 631, 14071, 116471, 24663654391, 1282510028791, ...
%C a(30) > 10^5.
%C Terms > 46 correspond to probable primes.
%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n!6-9&action=Search">PRP Records. Search for n!6-9.</a>
%H 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 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%e 16!6 - 9 = 16*10*4 - 8 = 631 is prime, so 16 is in the sequence.
%t MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
%t Select[Range[8, 50000], PrimeQ[MultiFactorial[#, 6] - 9] &]
%Y Cf. A007661, A037082, A084438, A123910, A242994.
%K nonn,more
%O 1,1
%A _Robert Price_, Jul 09 2017
%E a(27)-a(29) from _Robert Price_, Aug 03 2018
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