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 A307601 #21 May 14 2021 02:52:59
%S A307601 1,-1,0,0,-1,2,-4,7,-11,16,-21,26,-30,33,-33,28,-14,-13,59,-131,238,
%T A307601 -390,598,-873,1225,-1663,2194,-2822,3544,-4347,5202,-6059,6838,-7420,
%U A307601 7633,-7238,5911,-3226,-1365,8552,-19190,34320,-55189,83266,-120254,168094,-228958
%N A307601 Expansion of Product_{k>=1} (1 - x^k/(1 + x)).
%H A307601 Seiichi Manyama, <a href="/A307601/b307601.txt">Table of n, a(n) for n = 0..500</a>
%F A307601 G.f.: exp(-Sum_{k>=1} x^k * Sum_{d|k} 1/(d*(1+x)^d)).
%t A307601 m = 46; CoefficientList[Series[Product[1 - x^k/(1 + x), {k, 1, m}], {x, 0, m}], x] (* _Amiram Eldar_, May 14 2021 *)
%o A307601 (PARI) N=66; x='x+O('x^N); Vec(prod(k=1, N, 1-x^k/(1+x)))
%o A307601 (PARI) N=66; x='x+O('x^N); Vec(exp(-sum(k=1, N, x^k*sumdiv(k, d, 1/(d*(1+x)^d)))))
%Y A307601 Cf. A126348, A307599, A307602.
%K A307601 sign,look
%O A307601 0,6
%A A307601 _Seiichi Manyama_, Apr 18 2019