MathDB
Red numbers

Source: ITAMO 2019 #3

May 3, 2019
combinatoricsITAMO 2019

Problem Statement

Let n>2n>2 be an integer.. We want to color in red exactly n+1n+1 of the numbers 1,2,,2n1,2n1,2,\cdots,2n-1, 2n so that there do not exists three distinct red integers x,y,zx,y,z satisfying x+y=z.x+y=z. Prove that there is one and one only way to color the red numbers according to the given condition..