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pairs in a set

Source: Polish MO Second Round 1974 p1

September 8, 2024
combinatoricsSubsetssetSets

Problem Statement

Let Z Z be a set of n n elements. Find the number of such pairs of sets (A,B) (A, B) such that A A is contained in B B and B B is contained in Z Z . We assume that every set also contains itself and the empty set.
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