Game ensuring a base-2 representation is in S
Source: 2023 Thailand Online MO P10
February 12, 2023
combinatoricscombinatorial game
Problem Statement
Let be an even positive integer. Alice and Bob play the following game. Before the start of the game, Alice chooses a set containing integers and announces it to Bob. The players then alternate turns, with Bob going first, choosing that has not been chosen and setting the value of to either or . At the end of the game, when all of have been set, the expression is calculated. Determine the minimum such that Alice can always ensure that regardless of how Bob plays.