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 A306831 #20 May 23 2019 11:20:49
%S A306831 1,1,3,7,31,111,601,2773,27777,230401,2484811,22999791,254852863,
%T A306831 2615840527,29661610161,321837060301,5736337960321,86729871740673,
%U A306831 2360637009669907,39094827261418711,883743994410948831,14306422917625170991,301121907924200191753
%N A306831 Expansion of e.g.f. exp(Sum_{k>=1} x^(k^2)*(1 + x^(k^2))/k^2).
%F A306831 E.g.f.: Product_{k>=1} (1 - x^k)^((-1)^k*lambda(k)/k), where lambda() is the Liouville function (A008836).
%t A306831 nmax = 23; CoefficientList[Series[Exp[Sum[x^(k^2) (1 + x^(k^2))/k^2, {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
%t A306831 nmax = 23; CoefficientList[Series[Product[(1 - x^k)^((-1)^k LiouvilleLambda[k]/k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
%Y A306831 Cf. A008836, A053866, A205801, A308381.
%K A306831 nonn
%O A306831 0,3
%A A306831 _Ilya Gutkovskiy_, May 23 2019