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 A305633 #5 Jun 08 2018 13:53:49
%S A305633 0,0,1,1,-1,1,1,1,-1,1,1,1,-2,1,1,3,-1,1,2,1,-2,3,1,1,-3,1,1,1,-2,1,1,
%T A305633 1,-1,3,1,3,-3,1,1,3,-3,1,1,1,-2,4,1,1,-4,1,2,3,-2,1,3,3,-3,3,1,1,-4,
%U A305633 1,1,4,-1,3,1,1,-2,3,1,1,-3,1,1,4,-2,3,1,1,-4
%N A305633 Expansion of Sum_{r not a perfect power} x^r/(1 + x^r).
%t A305633 nn=100;
%t A305633 wadQ[n_]:=n>1&&GCD@@FactorInteger[n][[All,2]]==1;
%t A305633 ser=Sum[x^p/(1+x^p),{p,Select[Range[nn],wadQ]}];
%t A305633 Table[SeriesCoefficient[ser,{x,0,n}],{n,nn}]
%Y A305633 Cf. A000607, A001597, A007916, A048165, A081362, A091050, A303707, A304779, A304817, A305614, A305630-A305635.
%K A305633 sign
%O A305633 0,13
%A A305633 _Gus Wiseman_, Jun 07 2018