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product of each pair of 2 non-adjacent numbers is divisible by 2015x2016

Source: 2016 Saudi Arabia IMO TST , level 4, III p3

July 29, 2020
combinatoricsnumber theorydivisible

Problem Statement

Let n4n \ge 4 be a positive integer and there exist nn positive integers that are arranged on a circle such that: \bullet The product of each pair of two non-adjacent numbers is divisible by 201520162015 \cdot 2016. \bullet The product of each pair of two adjacent numbers is not divisible by 201520162015 \cdot 2016. Find the maximum value of nn