That formula is basically this one
But for the F side you would do X ≈ floor(sqrt(abs(F)*(N)))
Every A/B value in (E/F, 1) is a valid N, along with the factors of A/B. Along with any A/B values of any N cell in that E/F. The problem is divining which N to factor with, or which X in (E/F, 1) is the correct one to factor against.