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 A352839 #11 Apr 05 2022 21:20:35
%S A352839 1,1,6,39,370,4132,59288,990705,19577018,439550259,11142216938,
%T A352839 313147651821,9680830606850,325944181383936,11875777329091878,
%U A352839 465292113335910106,19507503314546762246,871248546067010133794,41295079536653463057146
%N A352839 Expansion of g.f. 1/(1 - Sum_{k>=1} sigma_k(k) * x^k).
%F A352839 a(0) = 1; a(n) = Sum_{k=1..n} sigma_k(k) * a(n-k).
%o A352839 (PARI) my(N=20, x='x+O('x^N)); Vec(1/(1-sum(k=1, N, sigma(k, k)*x^k)))
%o A352839 (PARI) a(n) = if(n==0, 1, sum(k=1, n, sigma(k, k)*a(n-k)));
%Y A352839 Cf. A129921, A180305, A320649.
%Y A352839 Cf. A023887, A352841, A352842.
%K A352839 nonn
%O A352839 0,3
%A A352839 _Seiichi Manyama_, Apr 05 2022