JBMO Shortlist 2021 C3
Source: JBMO Shortlist 2021
July 2, 2022
JuniorBalkanshorlist2021combinatoricsProcess
Problem Statement
We have a set of closed jars, each containing blue, yellow and red marbles with the number of marbles from each color being at least and at most . No two jars have exactly the same contents. Initially all jars are with the caps up. To flip a jar will mean to change its position from cap-up to cap-down or vice versa. It is allowed to choose a
triple of positive integers and flip all the jars whose number of blue, yellow and red marbles differ by not more than from , respectively. After moves all the jars turned out to be with the caps down. Find the number of all possible values of , if .