2006 Romanian NMO Problems/Grade 8/Problem 2
Problem
Let be a positive integer. Prove that there exists an integer
,
, and numbers
, such that
![$n = \sum_{1\leq i < j \leq k } a_ia_j$](http://latex.artofproblemsolving.com/c/3/f/c3f8748bf68501f3212d2a2fabd83d374f793ea2.png)
Solution
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