The answers to exercises marked [BB] can be found in the Back of the Book.[BB] Suppose a1,...

The answers to exercises marked [BB] can be found in the Back of the Book.

[BB] Suppose a1, a2, a3,… is a sequence of integers such that a1 = 0 and, for n > 1, an = n3 + an−1. Prove that for every integer n ≥ 1.