MathDB
No right-angled triangle

Source: Argentina TST 2009

May 15, 2009
inductionpigeonhole principlecombinatorics unsolvedcombinatorics

Problem Statement

On a 50×50 50 \times 50 board, the centers of several unit squares are colored black. Find the maximum number of centers that can be colored black in such a way that no three black points form a right-angled triangle.