MathDB
BMO Shortlist 2021 N7

Source: BMO Shortlist 2021

May 8, 2022
Balkanshortlist2021number theoryTriangle

Problem Statement

A super-integer triangle is defined to be a triangle whose lengths of all sides and at least one height are positive integers. We will deem certain positive integer numbers to be good with the condition that if the lengths of two sides of a super-integer triangle are two (not necessarily different) good numbers, then the length of the remaining side is also a good number. Let 55 be a good number. Prove that all integers larger than 22 are good numbers.