pawns are placed in a given grid
Source: ItaMO 2003, P5
February 13, 2012
combinatorics unsolvedcombinatorics
Problem Statement
In each lattice-point of an grid and in the centre of each of the formed unit squares a pawn is placed.a) Find all such grids with exactly pawns.
b) Prove that there are infinitely many positive integers for which therer is no grid containing exactly pawns.