Problem

Source: Indonesia TST 2009 Second Stage Test 3 P2

Tags: combinatorics proposed, combinatorics



Prove that there exists two different permutations $ (a_1,a_2,\dots,a_{2009})$ and $ (b_1,b_2,\dots,b_{2009})$ of $ (1,2,\dots,2009)$ such that \[ \sum_{i=1}^{2009}i^i a_i - \sum_{i=1}^{2009} i^i b_i\] is divisible by $ 2009!$.