 Examples of recursive definitions can be found intermittently in the history of ancient and medieval mathematics. A familiar illustration is the sequence \(F_i\) of Fibonacci numbers \(1,1,2,3,5,8,13, \ldots\) given by the recurrence \(F_0 = 1, F_1 = 1\) and \(F_{n} = F_{n-1} + F_{n-2}\) (see  Section 2.1.3).  The definition of this sequence has traditionally been attributed to the thirteenth century Italian mathematician Leonardo of Pisa (also known as Fibonacci) who introduced it in his Liber Abaci in the context of an example involving population genetics (see Fibonacci 1202 [2003, 404–405]). But descriptions of similar sequences can also be found in Greek, Egyptian, and Sanskrit sources dating as early as 700 BCE (see, e.g., Singh 1985).