IMO Shortlist 2009 problem N3
Dodao/la: arhiva2. travnja 2012.
be a non-constant function from the set of positive integers into the set of positive integer, such that
for all distinct positive integers
. Prove that there exist infinitely many primes
for some positive integer
Proposed by Juhan Aru, Estonia
Izvor: Međunarodna matematička olimpijada, shortlist 2009