This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A289547 #15 Nov 29 2018 17:21:44 %S A289547 6,7,9,15,21,27,29,321,327,333,567,1025,4263,4365,5175,5655,9221,9327, %T A289547 9681,19685,24777,57869,58737 %N A289547 Numbers k such that k!6 - 4 is prime, where k!6 is the sextuple factorial number (A085158 ). %C A289547 Corresponding primes are: 2, 3, 23, 401, 8501, 229631, 623641, ... %C A289547 a(24) > 10^5. %C A289547 Terms > 29 correspond to probable primes. %H A289547 Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n!6-4&action=Search">PRP Records. Search for n!6-4.</a> %H A289547 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 A289547 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a> %e A289547 15!6 - 4 = 15*9*3 - 4 = 401 is prime, so 15 is in the sequence. %t A289547 MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]]; %t A289547 Select[Range[4, 50000], PrimeQ[MultiFactorial[#, 6] - 4] &] %Y A289547 Cf. A007661, A037082, A084438, A123910, A242994. %K A289547 nonn,more %O A289547 1,1 %A A289547 _Robert Price_, Jul 07 2017 %E A289547 a(22)-a(23) from _Robert Price_, Aug 03 2018