Coloring a triangular arrangement of circles
Source: Cono Sur 2003 #5
November 18, 2015
combinatoricscono sur
Problem Statement
Let , where is a positive integer. A triangular arrangement of side is formed using circles with the same radius, as is shown in the figure for .
Determine, for each , the largest number of circles that can be colored red in such a way that there are no two mutually tangent circles that are both colored red.