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 A294404 #15 Aug 17 2021 10:11:01
%S A294404 1,-1,-9,-31,-23,3399,41311,473129,1284081,-79051537,-2447228249,
%T A294404 -52444297071,-712806368999,-2221410364681,331443685309647,
%U A294404 15068893004257049,460836352976093281,10298306504802529119,122928784866003823831,-3359583359629857247807
%N A294404 E.g.f.: exp(-Sum_{n>=1} sigma_2(n) * x^n).
%H A294404 Seiichi Manyama, <a href="/A294404/b294404.txt">Table of n, a(n) for n = 0..426</a>
%F A294404 a(0) = 1 and a(n) = (-1) * (n-1)! * Sum_{k=1..n} k*A001157(k)*a(n-k)/(n-k)! for n > 0.
%F A294404 E.g.f.: Product_{k>=1} (1 - x^k)^f(k), where f(k) = (1/k) * Sum_{j=1..k} gcd(k,j)^3. - _Ilya Gutkovskiy_, Aug 17 2021
%o A294404 (PARI) N=66; x='x+O('x^N); Vec(serlaplace(exp(-sum(k=1, N, sigma(k, 2)*x^k))))
%Y A294404 E.g.f.: exp(-Sum_{n>=1} sigma_k(n) * x^n): A294402 (k=0), A294403 (k=1), this sequence (k=2).
%Y A294404 Cf. A001157, A073592, A294362, A343497.
%K A294404 sign
%O A294404 0,3
%A A294404 _Seiichi Manyama_, Oct 30 2017