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 A309575 #29 Sep 22 2019 09:17:29
%S A309575 1,-1,-2,-2,-1,1,5,11,17,26,36,35,20,-5,-65,-221,-510,-897,-1379,
%T A309575 -2157,-3498,-5225,-6500,-6425,-4775,-1463,5951,25905,74833,173129,
%U A309575 334719,563200,876876,1363232,2208921,3621969,5631470,7896109,9725768,10374574,9340382,6104500,-1413334
%N A309575 Expansion of Product_{k>=1} (1 - (x*(1 + x))^k).
%F A309575 G.f.: exp(-Sum_{k>=1} sigma(k)*(x*(1+x))^k/k).
%t A309575 nmax = 40; CoefficientList[Series[Product[(1 - (x*(1+x))^k), {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Sep 22 2019 *)
%o A309575 (PARI) N=66; x='x+O('x^N); Vec(prod(k=1, N, 1-(x*(1+x))^k))
%o A309575 (PARI) N=66; x='x+O('x^N); Vec(exp(-sum(k=1, N, sigma(k)*(x*(1+x))^k/k)))
%Y A309575 Convolution inverse of A238441.
%Y A309575 Cf. A266108, A306565, A307501, A307548, A327671.
%K A309575 sign
%O A309575 0,3
%A A309575 _Seiichi Manyama_, Sep 21 2019