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 A307780 #7 Apr 28 2019 20:09:59
%S A307780 1,1,1,2,2,3,4,5,5,7,8,9,17,18,19,29,29,30,58,59,91,157,158,159,284,
%T A307780 317,318,445,573,574,1161,1162,1162,1676,1677,2830,4071,4072,4073,
%U A307780 8988,12113,12114,20134,20135,22183,32681,32682,32683,57072,73457,90265,114656,122848,122849,169533
%N A307780 a(1) = 1; a(n+1) = Sum_{d|n, n/d odd} a(d)^(n/d).
%F A307780 L.g.f.: log(Product_{n>=1} ((1 + a(n)*x^n)/(1 - a(n)*x^n))^(1/(2*n))) = Sum_{n>=1} a(n+1)*x^n/n.
%t A307780 a[n_] := a[n] = Sum[Boole[OddQ[(n - 1)/d]] a[d]^((n - 1)/d), {d, Divisors[n - 1]}]; a[1] = 1; Table[a[n], {n, 1, 55}]
%Y A307780 Cf. A127525, A307781.
%K A307780 nonn
%O A307780 1,4
%A A307780 _Ilya Gutkovskiy_, Apr 28 2019