OFFSET
1,6
COMMENTS
FORMULA
G.f.: Sum_{i = p*q, p prime, q prime} x^i/(1 - x^i) / Product_{j>=1} (1 - x^j).
EXAMPLE
a(6) = 3 because we have [6], [5, 1], [4, 2], [4, 1, 1], [3, 3], [3, 2, 1], [3, 1, 1, 1], [2, 2, 2], [2, 1, 1, 1, 1], [1, 1, 1, 1, 1, 1] and 1 + 0 + 1 + 1 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 3.
MATHEMATICA
nmax = 53; Rest[CoefficientList[Series[Sum[Floor[PrimeOmega[i]/2] Floor[2/PrimeOmega[i]] x^i/(1 - x^i), {i, 2, nmax}]/Product[1 - x^j, {j, 1, nmax}], {x, 0, nmax}], x]]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jan 25 2017
STATUS
approved