2012-2013 Winter OMO #33
Source:
January 16, 2013
Online Math Opengeometrygeometric transformationreflectioncombinatorial geometry
Problem Statement
Let be a positive integer. E. Chen and E. Chen play a game on the points of an lattice grid. They alternately mark points on the grid such that no player marks a point that is on or inside a non-degenerate triangle formed by three marked points. Each point can be marked only once. The game ends when no player can make a move, and the last player to make a move wins. Determine the number of values of between and (inclusive) for which the first player can guarantee a win, regardless of the moves that the second player makes.Ray Li