Tuymaada 2010, Junior League, Problem 4
Source:
July 18, 2010
combinatorics unsolvedcombinatoricsinvariant
Problem Statement
On a blackboard there are natural nonzero numbers. We define a "move" by erasing and with and replacing them with and , or we can choose to replace them by and if is divisible by 4.Knowing that in the beginning the numbers and have been erased, show that the original set of numbers cannot be attained again by any sequence of moves.