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existence of exactly n grid points (lattice) in a circle

Source: Norwegian Mathematical Olympiad 2009 - Abel Competition p3b

September 5, 2019
combinatoricscombinatorial geometrylattice pointscirclegeometrypoints

Problem Statement

Show for any positive integer nn that there exists a circle in the plane such that there are exactly nn grid points within the circle. (A grid point is a point having integer coordinates.)