Fix factorial: use recursive implementation

values.py

@@ -13,7 +13,6 @@ def pi(n):
     return pii
 
 def factorial(n):
-    r = 1
-    for i in range(n+1):
-        r *= i
-    return r
+    if n==0:
+        return 0
+    return n*factorial(n-1)