#lang racket
(define (show-line xs)
(for ([x xs]) (display (~a x #:width 4 #:align 'right)))
(newline))
(show-line (cons "" (range 1 13)))
(for ([y (in-range 1 13)])
(show-line (cons y (for/list ([x (in-range 1 13)])
(if (<= y x) (* x y) "")))))