from the IMO shortlist...
12:05
Slovenia Math Olympiad | 2005: Q2
16:44
The smallest such prime...
24:20
Too hard for the IMO? Too easy?
37:03
the equation Ramanujan couldn't solve!!
13:26
A Fun One from the Vietnamese IMO
12:27
Weak Spots of Functional Equations | International Mathematical Olympiad 2011 Shortlist A3
15:11
a floor equation.
21:04