The number *e* is a famous irrational number called Euler’s number after Leonhard Euler a Swiss Mathematician (1707 – 1783). Number *e* is considered to be one of the most important numbers in mathematics.

The first few digits are: 2.7182818284590452353602874713527… It has an infinite number of digits with no recurring pattern. It cannot be written as a simple fraction.

Number *e* is the limit of (1 + ^{1}/_{n})^{n} as n approaches infinity:

Number *e* is a mathematical constant that is the base of the natural logarithm: the unique number whose natural logarithm is equal to one. Find out more on https://en.wikipedia.org/wiki/E_(mathematical_constant).

In this challenge we will use a Python script to calculate an approximation of *e* using two different approaches:

- An iterative approach
- A recursive approach

#### Calculating *e* using an iterative approach

Euler’s number,

*e*, can also be calculated as the sum of the infinite series:

Complete your Python script to implement this infinite series using an iterative approach. (Method 2)

#### Calculating *e* using a recursive approach

A less common approach to calculate number

*e*is to use a continued fraction based on the following sequence:

Continued Fraction:

Complete your Python script to implement this continued fraction. (Method 3)

#### Extension Task:

This continued fraction for

*e*converges three times as quickly:

This continued fraction for e converges three times as quickly.

Complete your Python script to implement this continued fraction. (Method 4)