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 A281781 #21 May 29 2018 00:47:03
%S A281781 1,1,-1,2,-1,-2,6,-6,3,-1,-1,9,-18,23,-27,23,-1,-24,49,-89,121,-117,
%T A281781 96,-60,-18,138,-275,408,-525,592,-566,444,-181,-276,854,-1485,2154,
%U A281781 -2765,3157,-3131,2571,-1468,-301,2813,-5860,9153,-12386,15082,-16664,16558,-14125
%N A281781 Expansion of Product_{k>=1} (1 - x^(2*k))^(2*k)/(1 - x^(2*k-1))^(2*k-1).
%H A281781 Seiichi Manyama, <a href="/A281781/b281781.txt">Table of n, a(n) for n = 0..10000</a>
%F A281781 G.f.: exp(Sum_{k>=1} x^k/(k*(1 + x^k)^2)). - _Ilya Gutkovskiy_, May 28 2018
%t A281781 nmax = 50; CoefficientList[Series[Product[(1 - x^(2*k))^(2*k)/(1 - x^(2*k-1))^(2*k-1), {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Nov 09 2017 *)
%t A281781 nmax = 50; CoefficientList[Series[Product[(1 - x^(2*k))^(4*k)/(1 - x^k)^k, {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Nov 09 2017 *)
%t A281781 nmax = 50; CoefficientList[Series[Product[(1 + x^k)^(4*k)*(1 - x^k)^(3*k), {k, 1, nmax}], {x, 0, nmax}], x] (* _Vaclav Kotesovec_, Nov 09 2017 *)
%o A281781 (PARI) x='x+O('x^51); Vec(prod(k=1, 50, (1 - x^(2*k))^(2*k)/(1 - x^(2*k-1))^(2*k-1))) \\ _Indranil Ghosh_, Apr 14 2017
%Y A281781 Cf. A262811, A281683.
%K A281781 sign
%O A281781 0,4
%A A281781 _Seiichi Manyama_, Apr 14 2017