numbers of each color from 4 form a monotone subsequence
Source: Czech and Slovak MO, III A, 2005 p6
January 12, 2020
ColoringmonotoneSequencecombinatoricspermutation
Problem Statement
Decide whether for every arrangement of the numbers in a sequence one can color these numbers with at most four different colors in such a way that the numbers of each color form a monotone subsequence.