If A is a finite set of positive integers and a is in A, let f(a) denote

{ a / gcd(a, b) : b in A}. There is a set of n positive integers A with the property that the number of distinct integers in

Union[f(a) : a in A] is less than n. Find such a set.Source: April 1999 Monthly article by Granville and Roesler.© Copyright 1999 Stan Wagon. Reproduced with permission.

7 September 1999