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 A294388 #39 Aug 30 2025 11:17:31
%S A294388 1,1,11,223,12193,1548841,501460531,355752425239,558112176198305,
%T A294388 2023318561014654769,15928875457207423721731,
%U A294388 268023268481704204728199711,10084410400965244525857478169665,817174553170437003290060071895273113
%N A294388 a(n) = n! * [x^n] exp(Sum_{k=1..n} sigma_n(k) * x^k).
%H A294388 Seiichi Manyama, <a href="/A294388/b294388.txt">Table of n, a(n) for n = 0..75</a>
%t A294388 Table[n! * SeriesCoefficient[Exp[Sum[DivisorSigma[n,k] * x^k, {k,1,n}]],{x,0,n}], {n,0,20}] (* _Vaclav Kotesovec_, Aug 30 2025 *)
%Y A294388 Main diagonal of A294296.
%Y A294388 Cf. A252782.
%K A294388 nonn,changed
%O A294388 0,3
%A A294388 _Seiichi Manyama_, Oct 30 2017