Fibonacci

Leonardo of Pisa, who wrote under the pen name Fibonacci, may have been the greatest mathematician of the middle ages.  His text Liber Abaci introduced the Hindu-Arabic numeral system to Western Europe in 1202.  He is now most remembered for a trivial problem in that text counting the number of offspring of a pair of rabbits.  Lucas called the sequence of numbers discussed by that problem the Fibonacci numbers.

See Also: FibonacciNumber