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 A247866 #13 Feb 16 2025 08:33:23
%S A247866 2,7,14,16,22,23,26,40,43,47,58,62,70,107,265,292,439,874,982,1063,
%T A247866 1150,2506,3578,3775,7679,10024,42625,46714
%N A247866 Numbers k such that k!3 + 3^4 is prime.
%C A247866 Large terms correspond to probable primes.
%C A247866 a(29) > 50000.
%H A247866 Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=n!3+81&action=Search">PRP Records. Search for n!3+81</a>
%H A247866 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 A247866 OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%H A247866 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Multifactorial.html">Multifactorial</a>.
%e A247866 7!3 + 81 = 7*4*1 + 81 = 109 is prime, so 7 is in the sequence.
%t A247866 MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]];
%t A247866 lst={};Do[If[PrimeQ[MultiFactorial[n, 3] + 81], AppendTo[lst, n]], {n, 100}];lst
%Y A247866 Cf. A007661, A037082, A084438, A243078.
%K A247866 nonn,more
%O A247866 1,1
%A A247866 _Robert Price_, Sep 25 2014