In mathematics, the Fibonacci sequence is a serial arrangement
of numbers beginning with two 1's. Each new term is generated as the sum of
the previous two: 1, 1, 2, 3, 5, 8, 13, . . . The 13th-century mathematician
Leonardo of Pisa (c. 1170 - after 1240), also known as Fibonacci, discovered
the sequence. Applications can be found in botany and other natural sciences.
Examples of Fibonacci number ratios: the form of certain shells, the spiral
growth of branches, the scheme of arrangement of needles, cone scales or of
sunflower seeds.