## Fibonacci Number

The Fibonacci numbers in a sequence of numbers defined by the recurrence relation

(= (fibonacci (+ A (2))) (+ (fibonacci A) (fibonacci (+ A (1))))) /edit/peano/peano_thms.gh/df-fibRecurse

This sequence was introduced by Leonardo Fibonacci.

### Examples

The first (+ (10) (5)) numbers in the Fibonacci sequence are:

(0) /edit/peano/peano_thms.gh/fibonacci0, (1) /edit/peano/peano_thms.gh/fibonacci1, (1) /edit/peano/arithmetic.gh/fibonacci2, (2) /edit/peano/arithmetic.gh/fibonacci3, (3) /edit/peano/arithmetic.gh/fibonacci4, (5) /edit/peano/arithmetic.gh/fibonacci5, (8) /edit/peano/arithmetic.gh/fibonacci6, (+ (10) (3)) /edit/peano/arithmetic.gh/fibonacci7, (+ (* (2) (10)) (1)) /edit/peano/arithmetic.gh/fibonacci8, (+ (* (3) (10)) (4)) /edit/peano/arithmetic.gh/fibonacci9, (+ (* (5) (10)) (5)) /edit/peano/arithmetic.gh/fibonacci10, (+ (* (8) (10)) (9)) /edit/peano/arithmetic.gh/fibonacci11, (+ (* (10) (10)) (+ (* (4) (10)) (4))) /edit/peano/arithmetic.gh/fibonacci12, (+ (* (2) (* (10) (10))) (+ (* (3) (10)) (3))) /edit/peano/arithmetic.gh/fibonacci13, (+ (* (3) (* (10) (10))) (+ (* (7) (10)) (7))) /edit/peano/arithmetic.gh/fibonacci14, (+ (* (6) (* (10) (10))) (10)) /edit/peano/arithmetic.gh/fibonacci15