reverse any 5 coins in a row from a total of 289 coins in a 17x17 grid
Source: 2009 Swedish Mathematical Competition p6
April 27, 2021
combinatoricsgame
Problem Statement
On a table lie coins that form a square array . All coins are facing with the crown up. In one move, it is possible to reverse any five coins lying in a row: vertical, horizontal or diagonal. Is it possible that after a number of such moves, all the coins to be arranged with tails up?