(defun lotto-numbers (p n)
  (let ((balls (make-array n)))
    (dotimes (i n)
      (setf (aref balls i) (1+ i)))
    (dotimes (i p)
      (rotatef (aref balls (random n)) (aref balls (decf n))))
    (subseq balls n)))


(lotto-numbers 6 42)
--> #(28 13 42 33 2 12)