Each week Manhattan GMAT posts a GMAT question on our blog and follows up with the answer the next day. Are you up for the challenge?
If, for all integers n ≥ 1, xn is the probability of selecting at random an integer with an odd number of unique positive factors from among the positive integers less than or equal to n2, then the sum of the first 5 values of xn is
(A) less than 1
(B) between 1 and 2
(C) between 2 and 3
(D) between 3 and 4
(E) greater than 4