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 A245015 #26 Mar 10 2015 04:36:17
%S A245015 1,5,14,15,23,54,56,87,95,264,270,280,354,376,406,418,435,459,478,537,
%T A245015 623,649,667,719,1560,1740,1824,1836,1992,2148,2214,2262,2296,2392,
%U A245015 2470,2492,2514,2528,2596,2668,2876,3058,3154,3471,3567,3777,3835,3895,4147,4195,4199
%N A245015 Numbers n such that sigma(n) is a factorial.
%C A245015 Numbers n such that A000203(n) is in A000142.
%H A245015 Jens Kruse Andersen, <a href="/A245015/b245015.txt">Table of n, a(n) for n = 1..10000</a>
%e A245015 sigma(5) is 6 which is 3!, so 5 is n the sequence.
%t A245015 Select[Range[4000], MemberQ[Range[8]!, DivisorSigma[1, #]] &] (* _Alonso del Arte_, Sep 24 2014 *)
%o A245015 (PARI) isok(n) = {if (n==1, return (1)); s = sigma(n); f = 1; for (k=2, s, f *= k; if (f == s, return (1)); if (f > s, return (0)););} \\ _Michel Marcus_, Mar 09 2015
%Y A245015 Cf. A000203, A000142, A055486.
%K A245015 nonn
%O A245015 1,2
%A A245015 _Alex Ratushnyak_, Sep 16 2014