(defun hailstone (len)
    (loop for x = len
             then (if (evenp x)
                         (/ x 2)
                         (+ 1 (* 3 x)))
        collect x until (= x 1)))

;; Must be tail recursive
(defun max-hailstone-start (limit mx curr)
   (declare (xargs :mode :program))
   (if (zp limit)
       (mv mx curr)
       (let ((new-mx (len (hailstone limit))))
          (if (> new-mx mx)
              (max-hailstone-start (1- limit) new-mx limit)
              (max-hailstone-start (1- limit) mx curr)))))