The Rabbit Problem

In 1202, Italian mathematician Leonardo of Pisa (nicknamed Fibonacci) posed a puzzle about breeding rabbits. How many pairs exist after twelve months if each pair produces a new pair every month starting from their second month? The answer follows the sequence: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144.

Each number is the sum of the two before it. This simple rule — add the last two to get the next — produces a sequence that appears throughout nature with surprising regularity, from flower petals to the arrangement of seeds in a sunflower head.