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A289696 Numbers k such that k!6 - 18 is prime, where k!6 is the sextuple factorial number (A085158).

%I A289696 #14 Aug 10 2019 12:39:34
%S A289696 11,13,23,25,35,85,89,91,103,127,161,265,295,385,605,719,913,1379,
%T A289696 1423,1481,1603,2129,2603,3893,4739,6461,7249,7549,8149,10633,14447,
%U A289696 27463,30323,33991,35821,42221,46525,59057
%N A289696 Numbers k such that k!6 - 18 is prime, where k!6 is the sextuple factorial number (A085158).
%C A289696 Corresponding primes are: 37, 73, 21487, 43207, 21827557, 11510631741140058401857, ...
%C A289696 a(39) > 10^5.
%C A289696 Terms > 35 correspond to probable primes.
%H A289696 Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n!6-18&amp;action=Search">PRP Records. Search for n!6-18.</a>
%H A289696 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 A289696 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%e A289696 13!6 - 18 = 13*7 - 18 = 73 is prime, so 13 is in the sequence.
%t A289696 MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];
%t A289696 Select[Range[9, 50000], PrimeQ[MultiFactorial[#, 6] - 18] &]
%t A289696 Select[Range[11,60000],PrimeQ[Times@@Range[#,1,-6]-18]&] (* _Harvey P. Dale_, Aug 10 2019 *)
%Y A289696 Cf. A007661, A037082, A084438, A123910, A242994.
%K A289696 nonn,more
%O A289696 1,1
%A A289696 _Robert Price_, Jul 09 2017
%E A289696 a(38) from _Robert Price_, Aug 03 2018