(define nra (make-vector 2))

(define (r k) (if (> k 0) (let* (
     (a 0)
     (nextrandom (lambda () (set! a (modulo (+ (* a 23) 3) 1000)) a)))
  (vector-set! nra (- k 1) nextrandom) (r (- k 1)))

  (begin
  (write(list ((vector-ref nra 0)) ((vector-ref nra 0)) ((vector-ref nra 0))))
  (write(list ((vector-ref nra 1)) ((vector-ref nra 1)) ((vector-ref nra 1))))
  ((vector-ref nra 1))
  (let lp ((n 0)) (if (not (= ((vector-ref nra 0)) ((vector-ref nra 1))))
        (begin ((vector-ref nra 1)) (lp (+ n 1)))
        (write n))))
    ))

(r 2) ; => (3 72 659)(3 72 659)99

; Alternatively

(let* ((mi (lambda() (let ((a 0)) (lambda () (set! a (modulo (+ (* a 23) 3) 1000)) a))))
       (a (mi))(b (mi)))
     (write(list (a) (a) (a)))
     (write(list (b) (b) (b)))
     (b)
  (let lp ((n 0)) (if (not (= (a) (b))) (begin (b) (lp (+ n 1))) n)))