IMO Shortlist 2011 problem N4
Dodao/la: arhiva23. lipnja 2013.
For each positive integer
be the largest odd divisor of
Determine all positive integers
for which there exists a positive integer
such that all the differences
are divisible by 4.
Proposed by Gerhard Wöginger, Austria
Izvor: Međunarodna matematička olimpijada, shortlist 2011