OFFSET
0,5
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..10000
Eric Weisstein's World of Mathematics, Prime Factor
FORMULA
G.f.: Product_{k>=1} 1/(1 - x^A028260(k)).
EXAMPLE
a(8) = 4 because we have [6, 1, 1], [4, 4], [4, 1, 1, 1, 1] and [1, 1, 1, 1, 1, 1, 1, 1].
MAPLE
with(numtheory):
a:= proc(n) option remember; `if`(n=0, 1, add(a(n-j)*add(
`if`(bigomega(d)::odd, 0, d), d=divisors(j)), j=1..n)/n)
end:
seq(a(n), n=0..80); # Alois P. Heinz, May 04 2017
MATHEMATICA
nmax = 60; CoefficientList[Series[Product[1/(1 - Boole[EvenQ[PrimeOmega[k]]] x^k), {k, 1, nmax}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, May 04 2017
STATUS
approved