The first 89 natural numbers in Zeckendorf form. Each rectangle has a Fibonacci number Fj as width (blue number in the center) and Fj−1 as height. The vertical bands have width 10. In mathematics, Zeckendorf's theorem, named after Belgian amateur mathematician Edouard Zeckendorf, is a theorem about the representation of integers as sums of Fibonacci numbers. Zeckendorf's theorem states that every