International Zhautykov olympiad 2014 problem 3
Source:
January 14, 2014
rationumber theoryrelatively primecombinatorics proposedcombinatorics
Problem Statement
Given are 100 different positive integers. We call a pair of numbers good if the ratio of these numbers is either 2 or 3. What is the maximum number of good pairs that these 100 numbers can form? (A number can be used in several pairs.)Proposed by Alexander S. Golovanov, Russia