Update Fibonacci.fs (#20)

added a function to get the nth Fibonacci number

Author: Hogosha42

Algorithms/Math/Fibonacci.fs

@@ -4,4 +4,10 @@ module Fibonacci =
     let rec PrintSerie (one: int) (two: int) =
         let fibo = one + two
         System.Console.WriteLine fibo
-        PrintSerie two fibo
+        PrintSerie two fibo
+        
+    let rec NthFibonacci (n: int): int =
+        match n with
+            | 0 -> 0
+            | 1 -> 1
+            | n -> NthFibonacci (n-1) + NthFibonacci (n-2)