DouKaku?

(define (convert n)
  (let* ((nums "ABCDEFGHIJKLMNOPQRSTUVWXYZ")
	 (digit (string (string-ref nums (remainder (- n 1) (string-length nums)))))
	 (n (quotient (- n 1) (string-length nums))))
    (if (not (zero? n))
	(string-append (convert n) digit)
        digit)))

(let loop ((n 1) (m 1000))
  (cond ((<= n m)
         (display (convert n))
         (and (not (= n m)) (display ", "))
         (loop (+ n 1) m))
        (else (display #\newline))))