Fibonacci was a mathematician who published a book. The entire purpose of the book was to show how much easier it is to do mathematics using Arabic numerals, as opposed to Roman numerals. One example he gave was a simple list of numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89... et cetera. The sequence is formed by adding the two most recent numbers to get the next number.