(defun boolean-values (n)
  (let ((result '((t) (nil))))
    (dotimes (i (1- n) result)
      (let ((new-result '()))
        (dolist (thing result)
          (push (cons nil thing) new-result)
          (push (cons t thing) new-result))
        (setf result new-result)))))



CL-USER> (boolean-values 3)
((T NIL T) (NIL NIL T) (T T T) (NIL T T) 
 (T NIL NIL) (NIL NIL NIL) (T T NIL) (NIL T NIL))