Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #5 Jun 08 2018 13:53:49
%S 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 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 1,1,4,-1,3,1,1,-2,3,1,1,-3,1,1,4,-2,3,1,1,-4
%N Expansion of Sum_{r not a perfect power} x^r/(1 + x^r).
%t nn=100;
%t wadQ[n_]:=n>1&&GCD@@FactorInteger[n][[All,2]]==1;
%t ser=Sum[x^p/(1+x^p),{p,Select[Range[nn],wadQ]}];
%t Table[SeriesCoefficient[ser,{x,0,n}],{n,nn}]
%Y Cf. A000607, A001597, A007916, A048165, A081362, A091050, A303707, A304779, A304817, A305614, A305630-A305635.
%K sign
%O 0,13
%A _Gus Wiseman_, Jun 07 2018