MathDB
local champion integers

Source: IMO Shortlist 2006, Number Theory 6, AIMO 2007, TST 1, P3

June 28, 2007
number theoryrelatively primegreatest common divisorIMO Shortlist

Problem Statement

Let a>b>1 a > b > 1 be relatively prime positive integers. Define the weight of an integer c c, denoted by w(c) w(c) to be the minimal possible value of |x| \plus{} |y| taken over all pairs of integers x x and y y such that ax \plus{} by \equal{} c. An integer c c is called a local champion if w(c)w(c±a) w(c) \geq w(c \pm a) and w(c)w(c±b) w(c) \geq w(c \pm b).
Find all local champions and determine their number.
Proposed by Zoran Sunic, USA