OFFSET
0,6
LINKS
Amiram Eldar, Table of n, a(n) for n = 0..10000
Eric Weisstein's World of Mathematics, Distinct Prime Factors
FORMULA
G.f.: Product_{k>=1} (1 + x^A030230(k)).
EXAMPLE
a(9) = 4 because we have [9], [7, 2], [5, 4] and [4, 3, 2].
MATHEMATICA
nmax = 70; CoefficientList[Series[Product[1 + Boole[OddQ[PrimeNu[k]]] x^k, {k, 1, nmax}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, May 04 2017
STATUS
approved