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Ways to Place Counters on 2mx2n board

Source: 2019 Canadian Mathematical Olympiad Problem 3

March 28, 2019
combinatoricstilingscheckerboardcombinatorics solvedgridsBijectionsinduction

Problem Statement

You have a 2m2m by 2n2n grid of squares coloured in the same way as a standard checkerboard. Find the total number of ways to place mnmn counters on white squares so that each square contains at most one counter and no two counters are in diagonally adjacent white squares.