MathDB
Number Theory with game

Source: Balkan MO Shortlist 2020 N2

September 14, 2021
number theory

Problem Statement

A number of NN children are at a party and they sit in a circle to play a game of Pass and Parcel. Because the host has no other form of entertainment, the parcel has infinitely many layers. On turn ii, starting with i=1i=1, the following two things happen in order: (1)(1) The parcel is passed i2i^2 positions clockwise; and (2)(2) The child currently holding the parcel unwraps a layer and claims the prize inside. For what values of NN will every chidren receive a prize? Patrick WinterUnited KingdomPatrick \ Winter \, United \ Kingdom