The first two numbers in the Fibonacci sequence are 1, 1 and every number after the first two is the sum of the two preceding ones

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ............

The Fibonacci sequence appears in Indian mathematics, in connection with Sanskrit prosody. Susantha Goonatilake writes that the development of the Fibonacci sequence "is attributed in part to Pingala (200 BC), later being associated with Virahanka (c. 700 AD), Gopāla (c. 1135), and Hemachandra (c. 1150) The Fibonacci sequence is named after Italian mathematician Leonardo of Pisa, known as Fibonacci. Outside India, the Fibonacci sequence first appears in the book Liber Abaci (1202) by Fibonacci. Fibonacci considers the growth of an idealized (biologically unrealistic) rabbit population, assuming that: a newly born pair of rabbits, one male, one female, are put in a field; rabbits are able to mate at the age of one month so that at the end of its second month a female can produce another pair of rabbits; rabbits never die and a mating pair always produces one new pair (one male, one female) every month from the second month on. The puzzle that Fibonacci posed was: how many pairs will there be in one year?