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 A280197 #10 Feb 16 2025 08:33:38
%S A280197 1,0,1,1,1,3,3,6,8,12,20,28,45,68,102,159,238,367,557,849,1298,1973,
%T A280197 3015,4592,7002,10679,16276,24822,37841,57696,87971,134119,204497,
%U A280197 311783,475370,724786,1105053,1684853,2568837,3916642,5971587,9104711,13881698,21165024,32269721,49200718,75014949,114373158,174381511
%N A280197 Expansion of 1/(1 - Sum_{k>=2} mu(k)^2*x^k), where mu(k) is the Moebius function (A008683).
%C A280197 Number of compositions (ordered partitions) into squarefree parts > 1 (A144338).
%H A280197 Robert Israel, <a href="/A280197/b280197.txt">Table of n, a(n) for n = 0..5456</a>
%H A280197 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Squarefree.html">Squarefree</a>
%H A280197 <a href="/index/Com#comp">Index entries for sequences related to compositions</a>
%F A280197 G.f.: 1/(1 - Sum_{k>=2} mu(k)^2*x^k).
%e A280197 a(5) = 3 because we have [5], [3, 2] and [2, 3].
%p A280197 N:= 100: # for a(0)..a(N)
%p A280197 g:= 1/(1-add(numtheory:-mobius(k)^2*x^k, k=2..N)):
%p A280197 S:= series(g,x,N+1):
%p A280197 seq(coeff(S,x,j),j=0..N); # _Robert Israel_, Dec 29 2016
%t A280197 nmax = 48; CoefficientList[Series[1/(1 - Sum[MoebiusMu[k]^2 x^k, {k, 2, nmax}]), {x, 0, nmax}], x]
%Y A280197 Cf. A005117, A008683, A073576, A144338, A280127, A280194.
%K A280197 nonn
%O A280197 0,6
%A A280197 _Ilya Gutkovskiy_, Dec 28 2016