MathDB
TOT 2000 Autumn AJ4 mark 31 on 8x8 chessboard

Source:

May 10, 2020
combinatoricsChessboardtable

Problem Statement

In how many ways can 3131 squares be marked on an 8×88 \times 8 chessboard so that no two of the marked squares have a common side?
(R Zhenodarov)