The sides of a 99-gon are initially colored so that consecutive sides are red, blue, red, blue, …, red, blue, yellow. We make a sequence of modifications in the coloring, changing the color of one side at a time to one of the three given colors (red, blue, yellow), under the constraint that no two adjacent sides may be the same color. By making a sequence of such modifications, is it possible to arrive at the coloring in which consecutive sides
are red, blue, red, blue, red, blue, …, red, yellow, blue? invariantabstract algebramodular arithmeticquadraticsgroup theorycombinatorics unsolvedcombinatorics