MathDB
Combinatorics

Source: Greece Archimedes Junior 2019

March 16, 2020
combinatorics

Problem Statement

In the table are written the positive integers 1,2,3,...,20181, 2,3,...,2018. John and Mary have the ability to make together the following move: They select two of the written numbers in the table, let a,ba,b and they replace them with the numbers 5a2b5a-2b and 3a4b3a-4b. John claims that after a finite number of such moves, it is possible to triple all the numbers in the table, e.g. have the numbers: 3,6,9,...,60543, 6, 9,...,6054. Mary thinks a while and replies that this is not possible. Who of them is right?