Problem A. 423. (March 2007)
A. 423. Find all positive integers n for which the numbers can be colored with n colors such that each color is used exactly twice and each of the numbers appear exactly once as the difference between two numbers with the same color.
German competition problem
Deadline expired on April 16, 2007.
9 students sent a solution. 5 points: Hujter Bálint, Korándi Dániel, Lovász László Miklós, Nagy 235 János, Sümegi Károly, Tomon István. 4 points: Nagy 314 Dániel. 3 points: 1 student. Unfair, not evaluated: 1 solution.