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USAMO 1984 Problem 2 - Geometric Mean

Source: USAMO 1984 Problem 2

August 16, 2011
AMCUSA(J)MOUSAMOnumber theory unsolvednumber theory

Problem Statement

The geometric mean of any set of mm non-negative numbers is the mm-th root of their product.
  (\text{i})  For which positive integers nn is there a finite set SnS_n of nn distinct positive integers such that the geometric mean of any subset of SnS_n is an integer?   (\text{ii})  Is there an infinite set SS of distinct positive integers such that the geometric mean of any finite subset of SS is an integer?