paint a finite number of cells black in an infinite white plane of square cells
Source: Tournament of Towns, Senior A-Level Paper, Spring 2020 , p7
June 3, 2020
Coloringcombinatoricstable
Problem Statement
Consider an infinite white plane divided into square cells. For which it is possible to paint a positive finite number of cells black so that on each horizontal, vertical and diagonal line of cells there is either exactly black cells or none at all?A. Dinev, K. Garov, N Belukhov