#| BEGIN (Write your solution here) |#
(define (cont-frac n d k)
  (define (iter i n d k)
    (if (= i k)
        (/ (n i) (d i))
        (/ (n i) (+ (d i) (iter (+ i 1) n d k)))))
  (iter 1 n d k))


(define (pattern n)
  (define (iter acc i)
    (cond ((= (remainder i 3) 2)
           (if (= i n)
               (* (- i acc) 2)
               (iter (+ acc 2) (+ i 1))))
          (else
           (if (= i n)
               1
               (iter acc (+ i 1))))))
  (iter 1 1))

(define (e n)
  (+ 2 (cont-frac (lambda (x) 1.0)
             pattern
             n)))
#| END |#