Write a program that plays every possible tic-tac-toe game, and then prints the number of valid games

tictacttoe.clj

(defn end? [[x1 x2 x3 x4 x5 x6 x7 x8 x9]]
  (or
    (and (some? x1) (= x1 x2 x3))
    (and (some? x4) (= x4 x5 x6))
    (and (some? x7) (= x7 x8 x9))
    (and (some? x1) (= x1 x4 x7))
    (and (some? x2) (= x2 x5 x8))
    (and (some? x3) (= x3 x6 x9))
    (and (some? x1) (= x1 x5 x9))
    (and (some? x3) (= x3 x5 x7))
    (and (some? x1) (some? x2) (some? x3) (some? x4) (some? x5) (some? x6) (some? x7) (some? x8) (some? x9))))

(def *games (atom 0))

(defn make-move [start sym]
  (doseq [i (range 0 9)
          :when (nil? (nth start i))
          :let [end (assoc start i sym)]]
    (if (end? end)
      (swap! *games inc)
      (make-move end (if (= sym :x) :o :x)))))

(make-move [nil nil nil nil nil nil nil nil nil] :x)

(println @*games)