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 A330494 #16 Dec 16 2019 11:40:37
%S A330494 1,4,19,129,1018,9912,111074,1416398,20295208,323437728,5657339928,
%T A330494 107765338920,2223272444976,49399021063584,1175549092374672,
%U A330494 29822113966614768,803485297880792064,22917198585269729664,689927737384840662144,21861972842959846530432
%N A330494 a(n) = Sum_{k=1..n} (-1)^(n-k) * Stirling1(n,k) * (k-1)! * sigma(k), where sigma = A000203.
%H A330494 Vaclav Kotesovec, <a href="/A330494/b330494.txt">Table of n, a(n) for n = 1..400</a>
%F A330494 E.g.f.: Sum_{k>=1} log(1/(1 - x))^k / (k * (1 - log(1/(1 - x))^k)).
%F A330494 a(n) ~ n! * Pi^2 * exp(n) / (6 * (exp(1) - 1)^(n+1)).
%t A330494 Table[Sum[(-1)^(n-k) * StirlingS1[n, k] * (k-1)! * DivisorSigma[1, k], {k, 1, n}], {n, 1, 20}]
%t A330494 nmax = 20; Rest[CoefficientList[Series[Sum[Log[1/(1 - x)]^k/(k (1 - Log[1/(1 - x)]^k)), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!]
%o A330494 (PARI) a(n) = sum(k=1, n, (-1)^(n-k)*stirling(n, k, 1)*(k-1)!*sigma(k)); \\ _Michel Marcus_, Dec 16 2019
%Y A330494 Cf. A330353, A330354, A330493, A330495.
%K A330494 nonn
%O A330494 1,2
%A A330494 _Vaclav Kotesovec_, Dec 16 2019