Applied numpy µ-tutorial

The tutorial is for anyone who wants to learn the applied side of Numpy.
As a toy problem, we will build a model to predict the next element of the following sequence: 1, 2, 4, 8, 16, 31, ?

The tutorial is divided into six lessons with increasing level of difficulty:
* Lesson 1. - What are numpy arrays?
* Lesson 2. - Accessing elements of the array.
* Lesson 3. - Numerical operations.
* Lesson 4. - Vectorization.
* Lesson 5. - Symbolic calculations.
* Lesson 6. - Predicting 1, 2, 4, 8, 16, 31, ?