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 A306565 #66 May 14 2021 02:53:52
%S A306565 1,-1,-2,-1,1,3,4,3,1,-2,-6,-8,-8,-8,-5,2,8,12,17,22,23,17,7,0,-7,-22,
%T A306565 -40,-51,-53,-49,-45,-42,-30,-4,30,65,90,100,112,137,157,152,120,71,
%U A306565 18,-33,-80,-125,-187,-275,-357,-401,-407,-380,-327,-269,-221,-171,-75,102,322,515,669,801
%N A306565 Expansion of Product_{k>=1} (1 - x^k * (1 + x)).
%H A306565 Seiichi Manyama, <a href="/A306565/b306565.txt">Table of n, a(n) for n = 0..1000</a>
%F A306565 G.f.: exp( - Sum_{k>=1} x^k * Sum_{d|k} (1+x)^d / d).
%t A306565 m = 63; CoefficientList[Series[Product[1 - x^k * (1 + x), {k, 1, m}], {x, 0, m}], x] (* _Amiram Eldar_, May 14 2021 *)
%o A306565 (PARI) N=66; x='x+O('x^N); Vec(prod(k=1, N, 1-x^k*(1+x)))
%o A306565 (PARI) N=66; x='x+O('x^N); Vec(exp(-sum(k=1, N, x^k*sumdiv(k, d, (1+x)^d/d))))
%Y A306565 Convolution inverse of A227681.
%Y A306565 Cf. A160571.
%K A306565 sign
%O A306565 0,3
%A A306565 _Seiichi Manyama_, Apr 16 2019