Fibonacci sequence

The Fibonacci sequence is the sequence 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ... generated by the rule f1=f2=1, fn+1=fn+fn−1f_{1} = f_{2} = 1,  f_{n+1} = f_{n} + f_{n-1}.
It was introduced by Fibonacci of Pisa in Liber abaci in a problem involving the growth of a population of rabbits.