France TST 2003 D1 Q2
Source:
March 2, 2013
analytic geometrymodular arithmeticnumber theory unsolvednumber theory
Problem Statement
A lattice point in the coordinate plane with origin is called invisible if the segment contains a lattice point other than . Let be a positive integer. Show that there exists a square with side length and sides parallel to the coordinate axes, such that all points in the square are invisible.