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eight different symbols

Source: 8-th Taiwanese Mathematical Olympiad 1999

January 22, 2007
inductioncombinatorics unsolvedcombinatorics

Problem Statement

There are eight different symbols designed on n2n\geq 2 different T-shirts. Each shirt contains at least one symbol, and no two shirts contain all the same symbols. Suppose that for any kk symbols (1k7)(1\leq k\leq 7) the number of shirts containing at least one of the kk symbols is even. Determine the value of nn.