2022 Alg/NT DIv 1 P5
Source:
February 28, 2022
algebranumber theory
Problem Statement
Grant is standing at the beginning of a hallway with infinitely many lockers, numbered, All of the lockers are initially closed. Initially, he has some set . Every step, for each element of , Grant goes through the hallway and opens each locker divisible by that is closed, and closes each locker divisible by that is open. Once he does this for all , he then replaces with the set of labels of the currently open lockers, and then closes every door again. After steps, has integers that divide . Find .Proposed by Oliver Hayman