Squarefree factors

Consider the number 54. 54 can be factored in 7 distinct ways into one or more factors larger than 1: 54, 2×27, 3×18, 6×9, 3×3×6, 2×3×9 and 2×3×3×3. If we require that the factors are all squarefree only two ways remain: 3×3×6 and 2×3×3×3.

Let's call Fsf(n) the number of ways n can be factored into one or more squarefree factors larger than 1, so Fsf(54)=2.

Let S(n) be ∑Fsf(k) for k=2 to n.

S(100)=193.

Find S(10 000 000 000).

Written by gamwe6 who lives and works in San Francisco building useful things. You should follow him on Twitter