(ns xmas)
(doseq [line (concat (take 9 (map #(apply str
(take (+ (rem % 3)
(int (/ % 3)))
(repeat "*")))
(range 20)))
(take 2 (repeat "*")))]
(println (format "%1$30s*%1$s" line)))
; *
; ***
; *****
; ***
; *****
; *******
; *****
; *******
; *********
; ***
; ***