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 A308392 #6 May 24 2019 06:49:26
%S A308392 1,1,3,7,37,141,871,4243,42057,285337,3008971,23292831,295839853,
%T A308392 2733811237,35818366767,360892885291,8394097115281,113063153955633,
%U A308392 2347668770502547,32362689647446327,744513384520939701,11439249110436735421,245772094687992577783,3860080495614830875587
%N A308392 Expansion of e.g.f. exp(x + 2 * Sum_{k>=1} x^(2^k)/2^k).
%F A308392 E.g.f.: Product_{k>=1} (1 - x^k)^((-1)^k*mu(k)/k).
%F A308392 E.g.f.: exp(-x)*g(x)^2, where g(x) = e.g.f. of A005388.
%t A308392 nmax = 23; CoefficientList[Series[Exp[x + 2 Sum[x^(2^k)/2^k, {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
%t A308392 nmax = 23; CoefficientList[Series[Product[(1 - x^k)^((-1)^k MoebiusMu[k]/k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
%Y A308392 Cf. A005388, A008683.
%K A308392 nonn
%O A308392 0,3
%A A308392 _Ilya Gutkovskiy_, May 24 2019