pyramid2.clj

(defn print-pyramid [n]
  (loop [i n, spaces (apply str (repeat (dec n) " ")), stars "*"]
    (println (str spaces stars))
    (when (> i 1)
      (recur (dec i) (.substring spaces 1) (str stars "**")))))

;; user=> (print-pyramid 10)
;;          *
;;         ***
;;        *****
;;       *******
;;      *********
;;     ***********
;;    *************
;;   ***************
;;  *****************
;; *******************