ASU 519 All Soviet Union MO 1990 bw color in 1990 x 1990 chessboard
Source:
August 14, 2019
Chessboardsquare tableColoringcombinatorics
Problem Statement
Can the squares of a chessboard be colored black or white so that half the squares in each row and column are black and cells symmetric with respect to the center are of opposite color?