MathDB
Math Prize 2017 Problem 7

Source:

September 26, 2017
Math Prize for Girls

Problem Statement

Let a1a_1, a2a_2, ... be an infinite sequence of integers such that 0akk0 \le a_k \le k for every positive integer kk and such that 2017=k=1akk!. 2017 = \sum_{k = 1}^\infty a_k \cdot k! \, . What is the value of the infinite series k=1ak\sum_{k = 1}^\infty a_k?