One pair of immortal, ever-breeding rabbits accidentally invented a famous number sequence
In his 1202 book Liber Abaci, Fibonacci posed a thought experiment: start with one newborn pair of rabbits, assume every pair matures in a month and produces one new pair every month after that, and assume no rabbit ever dies. How many pairs exist after twelve months?
Reveal the answer
377 pairs. Each month's total equals the sum of the two previous months, since last month's rabbits are all still there and only pairs mature enough to breed add new ones, generating the sequence 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377. Fibonacci wasn't trying to discover a famous number sequence, he was just illustrating arithmetic with a memorable example, but the ratios of consecutive terms converge on the golden ratio.
— Leonardo of Pisa (Fibonacci), Liber Abaci — 1202
Go deeper: get the book →