Fibonacci is the mathematician whose name is given to the sequence 1, 1, 2, 3, 5, 8.
Fibonacci was the nickname of Leonardo of Pisa, an Italian mathematician born around 1170. He introduced the sequence to many European readers in his book Liber Abaci, published in 1202. The book presented Hindu–Arabic numerals and calculation methods that were more efficient than the Roman numerals commonly used in medieval Europe.
In the sequence, each number after the first two is the sum of the preceding two numbers. Depending on convention, sequences may begin with 0, 1 or with 1, 1, so the indexing can vary even though the recurrence remains the same.
The sequence appears in mathematical models and in some natural growth patterns, although popular claims about its universal presence in nature are often overstated. Ratios of successive Fibonacci numbers approach the golden ratio, approximately 1.618, a connection that has influenced mathematics, art, and design.