MathDB
Nordic 2009 Problem

Source:

March 23, 2011
combinatorics unsolvedcombinatorics

Problem Statement

The integers 11, 22, 33, 44, and 55 are written on a blackboard. It is allowed to wipe out two integers aa and bb and replace them with a+ba + b and abab. Is it possible, by repeating this procedure, to reach a situation where three of the five integers on the blackboard are 20092009?