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 A288421 #23 Sep 08 2022 08:46:19
%S A288421 1,-1,-2,-2,1,5,4,10,6,-5,-20,-27,-37,-32,-18,23,82,128,190,185,143,
%T A288421 43,-160,-424,-662,-968,-1058,-971,-571,238,1326,2748,4195,5301,5930,
%U A288421 5473,3353,55,-5346,-12106,-19421,-26603,-31950,-33248,-29344,-17469,2343,30966
%N A288421 Expansion of Product_{k>=1} 1/(1 + x^k)^sigma(k).
%H A288421 Seiichi Manyama, <a href="/A288421/b288421.txt">Table of n, a(n) for n = 0..10000</a>
%F A288421 Convolution inverse of A192065.
%F A288421 a(0) = 1, a(n) = -(1/n)*Sum_{k=1..n} A288418(k)*a(n-k) for n > 0.
%F A288421 G.f.: exp(-Sum_{k>=1} sigma_2(k)*x^k/(k*(1 - x^(2*k)))). - _Ilya Gutkovskiy_, Oct 29 2018
%t A288421 nmax = 50; CoefficientList[Series[Product[1/(1+x^k)^DivisorSigma[1, k], {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Jun 09 2017 *)
%o A288421 (PARI) m=50; x='x+O('x^m); Vec(prod(k=1, m+2, 1/(1+x^k)^sigma(k))) \\ _G. C. Greubel_, Oct 29 2018
%o A288421 (Magma) m:=50; R<q>:=PowerSeriesRing(Rationals(), m); Coefficients(R! ( (&*[1/(1+q^k)^DivisorSigma(1,k): k in [1..(m+2)]]) )); // _G. C. Greubel_, Oct 29 2018
%Y A288421 Cf. A192065, A288418.
%Y A288421 Product_{k>=1} 1/(1 + x^k)^sigma_m(k): A288007 (m=0), this sequence (m=1), A288422 (m=2), A288423 (m=3).
%K A288421 sign
%O A288421 0,3
%A A288421 _Seiichi Manyama_, Jun 09 2017