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Friendly numbers

Source: Cono Sur Olympiad 2016, problem 6

August 28, 2017
number theorycono sur

Problem Statement

We say that three different integers are friendly if one of them divides the product of the other two. Let nn be a positive integer.
a) Show that, between n2n^2 and n2+nn^2+n, exclusive, does not exist any triplet of friendly numbers.
b) Determine if for each nn exists a triplet of friendly numbers between n2n^2 and n2+n+3nn^2+n+3\sqrt{n} , exclusive.