CombinatoricsDifficulty 7.0National Olympiad, round 2Find the answerHungary
Let k, l and m be positive integers. Let ABCDEF be a hexagon that has a center of symmetry whose angles are all 120∘ and let its sidelengths be AB=k, BC=l and CD=m. Let f(k,l,m) denote the number of ways we can partition hexagon ABCDEF into rhombi with unit sides and an angle of 120∘.
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