OFFSET
0,6
COMMENTS
Number of compositions (ordered partitions) into squarefree parts > 1 (A144338).
LINKS
Robert Israel, Table of n, a(n) for n = 0..5456
Eric Weisstein's World of Mathematics, Squarefree
FORMULA
G.f.: 1/(1 - Sum_{k>=2} mu(k)^2*x^k).
EXAMPLE
a(5) = 3 because we have [5], [3, 2] and [2, 3].
MAPLE
N:= 100: # for a(0)..a(N)
g:= 1/(1-add(numtheory:-mobius(k)^2*x^k, k=2..N)):
S:= series(g, x, N+1):
seq(coeff(S, x, j), j=0..N); # Robert Israel, Dec 29 2016
MATHEMATICA
nmax = 48; CoefficientList[Series[1/(1 - Sum[MoebiusMu[k]^2 x^k, {k, 2, nmax}]), {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 28 2016
STATUS
approved