OFFSET
0,5
FORMULA
G.f.: Product_{k>=1} (1 + mu(k)^2 * x^(2*k) / (1 - x^k)).
EXAMPLE
a(6) = 4 because we have [3, 3], [2, 2, 2], [2, 2, 1, 1] and [1, 1, 1, 1, 1, 1].
MATHEMATICA
nmax = 60; CoefficientList[Series[Product[1 + MoebiusMu[k]^2 x^(2 k)/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Nov 27 2020
STATUS
approved