sicp/1_10.sch

(define (A x y)
  (cond ((= y 0) 0)
	((= x 0) (+ 2 y))
	((= y 1) 2)
	(else (A (- x 1)
		 (A x (- y 1))))))

; 2+n
(define (f n)
  (A 0 n))

; 2*n
(define (g n)
  (A 1 n))

; 2^n
(define (h n)
  (A 2 n))

(define (k n)
  (* 5 n n))