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 A308461 #5 May 28 2019 19:29:27
%S A308461 1,1,1,1,13,61,181,421,15961,137593,682921,2498761,77344741,927575221,
%T A308461 6402167773,31881065581,4104839160241,68050288734961,609856397747281,
%U A308461 3857727706737553,222655237411428541,4351842324095032621,47276537013742616581,361153046139022585141
%N A308461 Expansion of e.g.f. exp(x + 2 * Sum_{k>=2} x^(2^k)/2^k).
%F A308461 E.g.f.: Product_{k>=1} (1 + (-x)^k)^((-1)^k*mu(k)/k).
%F A308461 E.g.f.: exp(-x*(1 + x))*g(x)^2, where g(x) = e.g.f. of A005388.
%t A308461 nmax = 23; CoefficientList[Series[Exp[x + 2 Sum[x^(2^k)/2^k, {k, 2, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
%t A308461 nmax = 23; CoefficientList[Series[Product[(1 + (-x)^k)^((-1)^k MoebiusMu[k]/k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
%Y A308461 Cf. A000321, A005388, A008683, A308392.
%K A308461 nonn
%O A308461 0,5
%A A308461 _Ilya Gutkovskiy_, May 28 2019