Solution to Exercise 1.38:

`(define (cont-frac n d k)`

(define (iter i sub-expr)

(if (= i 0)

sub-expr

(iter (- i 1) (/ (n i) (+ (d i) sub-expr)))))

(iter (- k 1) (/ (n k) (d k))))

```
```

`(define (e k)`

(+ (cont-frac (lambda (i) 1.0)

(lambda (i) (if (= (remainder (+ i 1) 3) 0)

(* 2 (/ (+ i 1) 3))

1.0))

k)

2))