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 A329099 #4 Nov 05 2019 01:02:13
%S A329099 1,-1,0,0,1,-2,1,0,2,-4,2,0,4,-10,7,0,7,-23,22,-6,14,-51,59,-24,31,
%T A329099 -113,152,-80,66,-244,383,-253,166,-521,930,-746,460,-1133,2219,-2082,
%U A329099 1314,-2494,5208,-5607,3788,-5622,12037,-14608,10830,-13145,27618,-37089,30350,-31914,63248,-92290
%N A329099 Expansion of 1 / (1 + Sum_{k>=1} mu(k)^2 * x^k).
%F A329099 G.f.: 1 / (1 + Sum_{k>=1} x^A005117(k)).
%t A329099 nmax = 55; CoefficientList[Series[1/(1 + Sum[MoebiusMu[k]^2 x^k, {k, 1, nmax}]), {x, 0, nmax}], x]
%t A329099 a[0] = 1; a[n_] := a[n] = -Sum[Boole[SquareFreeQ[k]] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 55}]
%Y A329099 Cf. A002121, A005117, A008683, A280194.
%K A329099 sign
%O A329099 0,6
%A A329099 _Ilya Gutkovskiy_, Nov 04 2019