Exercise 1.38: In 1737, the Swiss mathematician
Leonhard Euler published a memoir De Fractionibus Continuis, which
included a continued fraction expansion for 
  
    e
    −
    2
  
, where 
  e
 is the base
of the natural logarithms.  In this fraction, the 
  
    N
    i
  
 are all 1, and
the 
  
    D
    i
  
 are successively 1, 2, 1, 1, 4, 1, 1, 6, 1, 1, 8, ….
Write a program that uses your cont-frac procedure from Exercise 1.37 
to approximate 
  e
, based on Euler’s expansion.