MathDB
5x5 board with n in all cells

Source: Serbia JBMO TST 2022 P4

June 1, 2022
combinatorics

Problem Statement

Initially in every cell of a 5×55\times 5 board is the number 00. In one move you may take any cell of this board and add 11 to it and all of its adjacent cells (two cells are adjacent if they share an edge). After a finite number of moves, number nn is written in all cells. Find all possible values of nn.