First written in 1202 by Leonardo Fibonacci in his work Liber Abaci (Book of Calculation), the Fibonacci numbers are a sequence of numbers where each proceeding number is a product of the two preceding ones. The first set of numbers in the sequence are: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144... and so on. The Fibonacci numbers often appear in mathematics as well as natural biology.