MathDB
Maximise the cardinality of X

Source: Baltic Way 2003

November 6, 2010
combinatorics unsolvedcombinatorics

Problem Statement

A subset of XX of {1,2,3,…10000}\{1,2,3, \ldots 10000 \} has the following property: If a,ba,b are distinct elements of XX, then ab∉Xab\not\in X. What is the maximal number of elements in XX?
Back to ProblemsView on AoPS