A function f is defined by the rule that f(n) = n if n<3 and f(n) = f(n - 1) + 2f(n - 2) +
3f(n - 3) if n> 3. Write a procedure that computes f by means of a recursive process. Write a
procedure that computes f by means of an iterative process.



(defun f(n)
  (cond ( (< n 3) n)
	( (+ (f (- n 1))
	     (* (f (- n 2)) 2)
	     (* (f (- n 3)) 3)))))








(defun g(n)
  (defun iter-g(a b c count)
    ( if (= count n) c
	 (iter-g b
		 c
		 (+ c
			(* 2 b)
			(* 3 a))
		 (+ count 1))))
  (if (< n 3) n
      (iter-g 0 1 2 2)))
		 
    
CL-USER> (f 0)
0
CL-USER> (f 1)
1
CL-USER> (f 2)
2
CL-USER> (f 3)
4
CL-USER> (f 4)
11
CL-USER> (f 5)
25
CL-USER> (f 6)
59


CL-USER> (g 0)
0
CL-USER> (g 1)
1
CL-USER> (g 2)
2
CL-USER> (g 3)
4
CL-USER> (g 4)
11
CL-USER> (g 5)
25
CL-USER> (g 6)
59