Sum of all possible values of winning strategy in a game
Source: Bangladesh Mathematical Olympiad 2021 Problem 8
February 26, 2022
combinatorics
Problem Statement
Shakur and Tiham are playing a game. Initially, Shakur picks a positive integer not greater than . Then Tiham picks a positive integer strictly smaller than that.Then they keep on doing this taking turns to pick progressively smaller and smaller positive integers until some one picks . After that, all the numbers that have been picked so far are added up. The person picking the number wins if and only if this sum is a perfect square. Otherwise, the other player wins. What is the sum of all possible values of such that if Shakur starts with the number , he has a winning strategy?