OFFSET
9,2
FORMULA
G.f.: (Sum_{k>=1} mu(k)^2 * x^k)^9.
MAPLE
b:= proc(n, t) option remember;
`if`(n=0, `if`(t=0, 1, 0), `if`(t<1, 0, add(
`if`(numtheory[issqrfree](j), b(n-j, t-1), 0), j=1..n)))
end:
a:= n-> b(n, 9):
seq(a(n), n=9..45); # Alois P. Heinz, Feb 04 2021
MATHEMATICA
nmax = 45; CoefficientList[Series[Sum[MoebiusMu[k]^2 x^k, {k, 1, nmax}]^9, {x, 0, nmax}], x] // Drop[#, 9] &
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Feb 04 2021
STATUS
approved