anchor.diff:                     (collect i)
                      (collect (/ n i))))
           #'<))
  +
  +(defun proper-divisors (n)
  +  (remove n (divisors n)))
   
   (defun count-divisors (n)
     (* 2 (iterate (for i :from 1 :to (sqrt n))
  
positive.code:   ;; Find the sum of the digits in the number 100!
    (sum (digits (factorial 100))))
  
  
  ;;;; Tests --------------------------------------------------------------------
  (def-suite :euler)
  
negative.code:           (not (dividesp n 11))) nil)
      (t (definitely-palindrome-p n))))
  
  
  (defun sum (sequence &key key)
    (iterate (for n :in-whatever sequence)
             (sum (if key
                    (funcall key n)
                    n))))
  
  
  (defun divisors (n)
    (sort (iterate (for i :from 1 :to (sqrt n))
  