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Three sets having the same color

Source: Iran 3rd round 2012-Special Lesson exam-Part 2-P3

September 15, 2012
graph theorycombinatorics proposedcombinatorics

Problem Statement

Prove that if nn is large enough, then for each coloring of the subsets of the set {1,2,...,n}\{1,2,...,n\} with 13911391 colors, two non-empty disjoint subsets AA and BB exist such that AA, BB and ABA\cup B are of the same color.