IMO Shortlist 2009 problem N7


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2. travnja 2012.
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Let a and b be distinct integers greater than 1. Prove that there exists a positive integer n such that \left(a^n-1\right)\left(b^n-1\right) is not a perfect square.

Proposed by Mongolia
Izvor: Međunarodna matematička olimpijada, shortlist 2009