#lang sicp

(define (cont-frac n d k)
  (define (cf-acc n d k i)
    (if (= k i)
        (/ (n i) (d i))
        (/ (n i) (+ (d i) (cf-acc n d k (+ i 1))))))
  (cf-acc n d k 0))

(define (e k)
  (+ 2.0 (cont-frac (lambda (i) 1.0)
                    (lambda (i)
                      (if (= (remainder i 3) 1)
                          (* 2.0 (/ (+ i 2) 3))
                          1.0))
                    k)))