How many knights you can put on chess table $5 \times 5$ such that every one of them attacks exactly two other knights ?
Problem
Source: Regional Olympiad - Federation of Bosnia and Herzegovina 2017
Tags: chess, knights, arranging, combinatorics
Source: Regional Olympiad - Federation of Bosnia and Herzegovina 2017
Tags: chess, knights, arranging, combinatorics
How many knights you can put on chess table $5 \times 5$ such that every one of them attacks exactly two other knights ?