=+4.15. 2.18 1 Let F be the set of square-free integers-those integers not divisible by any perfect square. Let F, be the set of m such that p2 Im for no p ≤1, and show that D(F,) = Ilps/(1 -p-2). Show that P.(F, - F) ≤E>> (p 2, and con-

clude that the square-free integers have density II (1 - p-2) = 6/T2.