OFFSET
0,4
COMMENTS
Number of compositions (ordered partitions) into odd squarefree parts (A056911).
LINKS
Eric Weisstein's World of Mathematics, Squarefree
FORMULA
G.f.: 1/(1 - Sum_{k>=1} mu(2*k-1)^2*x^(2*k-1)).
EXAMPLE
a(4) = 3 because we have [3, 1], [1, 3] and [1, 1, 1, 1].
MATHEMATICA
nmax = 46; CoefficientList[Series[1/(1 - Sum[MoebiusMu[2 k - 1]^2 x^(2 k - 1), {k, 1, nmax}]), {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 28 2016
STATUS
approved