factorial in Racket

factorial.rkt

#lang racket

(define (factorial n)
  (define (i_factorial n acc)
    (if (= 0 n)
      acc
      (i_factorial (- n 1) (* n acc))))
  (i_factorial n 1))

(map (lambda (n)
       (printf "~a~n" (factorial n))) (list 1 12 123 1234 12345))