S-99-36

 (define (prime? x) 
   (if (<= x 1) #f 
       (let loop ((t (- x 1))) 
         (if (eq? t 1) #t 
             (and (not (eq? (modulo x t) 0)) 
             (loop (- t 1))))))) 
  
 (define (prime-factors x) 
   (if (= x 1) '() 
       (let loop ((t x) (c 2)) 
         (cond ((= t 1) '()) 
               ((and (= (modulo t c) 0) (prime? c)) 
                (cons c (loop (quotient t c) 2))) 
               (else (loop t (+ c 1))))))) 
  
 (define (prime-factors-mult x) 
   (let ((fs (prime-factors x))) 
     (let loop ((e (cdr fs)) (c (car fs)) (n 1)) 
       (cond ((null? e) (list (list c n))) 
             ((eq? (car e) c) (loop (cdr e) c (+ n 1))) 
             (else (cons (list c n) (loop (cdr e) (car e) 1)))))))