(defun lotto-numbers ()
  (let ((balls (mapcar (function 1+) (iota 42)))
        (draw '()))
    (dotimes (i 6 (nreverse draw))
      (let ((ball (elt balls (random (length balls)))))
        (setf balls (remove ball balls))
        (push ball draw)))))

(lotto-numbers)
--> (35 13 33 6 19 16)