Fibonacci Rabbits

In 1202 Fibonacci investigated how fast rabbits could breed. Suppose a pair of rabbits, one male and one female, start a family. Rabbits mature at the age of one month and a female produces a new pair of rabbits at the end of its second month. Suppose that the rabbits survive forever and that a female always produces one new pair (one male, one female) every month, giving the original pair and a new one.

Choose the number of months