MathDB
Levelable distribution of coins

Source: Centroamerican 2020, problem 2

October 28, 2020
combinatoricsCombinatorial games

Problem Statement

Suppose you have identical coins distributed in several piles with one or more coins in each pile. An action consists of taking two piles, which have an even total of coins among them, and redistribute their coins in two piles so that they end up with the same number of coins.
A distribution is levelable if it is possible, by means of 0 or more operations, to end up with all the piles having the same number of coins.
Determine all positive integers nn such that, for all positive integers kk, any distribution of nknk coins in nn piles is levelable.