Grains problem in Racket using a home-made stream

I did the Grains problem in Racket using a home-made stream:

	#lang racket
	(define (grains)
	(letrec
	([f
	(lambda (n)
	(cons n
	(lambda () (f (* 2 n)) )))])
	(f 1)))
	(define (stream-for-n-steps stream n)
	(letrec ([f
	(lambda(i stream-rest)
	(if (= i 0)
	empty
	(cons (car (stream-rest))
	(f (- i 1) (cdr (stream-rest))))))])
	(f n stream)))
	(define (square sqr-num)
	(last (stream-for-n-steps grains sqr-num)))
	(define total-grains
	(lambda ()
	(foldr + 0 (stream-for-n-steps grains 64))))

view raw grains.rkt hosted with ❤ by GitHub

The stream is the function grains which returns a pair containing the first value and the generator of the rest of the stream.

The stream-for-n-steps helper gets n values from the stream.

Probably there is a function to do this directly in Racket but I wanted to remember what we did in the Coursera Programming Languages course.

Now I want to do something similar in Clojure.