King attacks marked cells
Source: Russian TST 2017, Day 5 P1 (Group NG)
April 1, 2023
boardcombinatoricschess king
Problem Statement
What is the largest number of cells that can be marked on a board in such a way that a chess king from any cell attacks no more than two marked ones? (The cell on which a king stands is also considered to be attacked by this king.)