1-9 into 3x3 board, difference of digits in cells that share a side is <=3
Source: 2019 Chile National Olympiad level 2 p1
October 22, 2022
combinatorics
Problem Statement
A square of is subdivided into 9 small squares of . It is desired to distribute the nine digits in each small square of , a number in each small square. Find the number of different distributions that can be formed in such a way that the difference of the digits in cells that share a side in common is less than or equal to three. Two distributions are distinct even if they differ by rotation and/or reflection.