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 A294403 #14 Aug 17 2021 10:10:55
%S A294403 1,-1,-5,-7,1,839,4171,54305,102817,-4303441,-74521349,-1595325271,
%T A294403 -20768141855,-222701825737,1485790534411,65580347824529,
%U A294403 2880129557707201,67631429234674655,1543424936566399867,23542870556917468889,119940955037901088321
%N A294403 E.g.f.: exp(-Sum_{n>=1} sigma(n) * x^n).
%H A294403 Seiichi Manyama, <a href="/A294403/b294403.txt">Table of n, a(n) for n = 0..439</a>
%F A294403 a(0) = 1 and a(n) = (-1) * (n-1)! * Sum_{k=1..n} k*A000203(k)*a(n-k)/(n-k)! for n > 0.
%F A294403 E.g.f.: Product_{k>=1} (1 - x^k)^f(k), where f(k) = (1/k) * Sum_{j=1..k} gcd(k,j)^2. - _Ilya Gutkovskiy_, Aug 17 2021
%o A294403 (PARI) N=66; x='x+O('x^N); Vec(serlaplace(exp(-sum(k=1, N, sigma(k)*x^k))))
%Y A294403 E.g.f.: exp(-Sum_{n>=1} sigma_k(n) * x^n): A294402 (k=0), this sequence (k=1), A294404 (k=2).
%Y A294403 Cf. A000203, A010815, A069097, A294361.
%K A294403 sign
%O A294403 0,3
%A A294403 _Seiichi Manyama_, Oct 30 2017