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 A307777 #9 Apr 28 2019 20:09:36
%S A307777 1,1,-2,-1,1,2,-2,-1,0,-1,-2,-1,6,7,-7,-7,5,6,-8,-7,6,3,-3,-2,5,7,-15,
%T A307777 -16,26,27,-22,-21,12,9,-16,-16,28,29,-23,-18,9,10,-23,-22,28,21,-20,
%U A307777 -19,25,24,-31,-27,29,30,-23,-23,16,7,-35,-34,79,80,-60,-57,27,35,-50,-49,54,50,-41
%N A307777 a(1) = 1; a(n+1) = Sum_{d|n} (-1)^(n/d+d)*a(d).
%F A307777 G.f.: x * (1 - Sum_{n>=1} a(n)*(-x)^n/(1 + x^n)).
%F A307777 L.g.f.: log(Product_{n>=1} (1 + x^n)^((-1)^(n+1)*a(n)/n)) = Sum_{n>=1} a(n+1)*x^n/n.
%t A307777 a[n_] := a[n] = Sum[(-1)^((n - 1)/d + d) a[d], {d, Divisors[n - 1]}]; a[1] = 1; Table[a[n], {n, 1, 71}]
%t A307777 a[n_] := a[n] = SeriesCoefficient[x (1 - Sum[a[k] (-x)^k/(1 + x^k), {k, 1, n - 1}]), {x, 0, n}]; Table[a[n], {n, 1, 71}]
%Y A307777 Cf. A003238, A281487, A307776, A307778, A307779.
%K A307777 sign
%O A307777 1,3
%A A307777 _Ilya Gutkovskiy_, Apr 28 2019