# All Lessons

## Data Structures

## Encoding & Compression

## Number Theory

### Number Orders

A description of number orders in modular arithmetic.

### Reciprocity

A description of quadratic reciprocity in modular arithmetic and an introduction to generalized reciprocity.

### Operations

Properties of addition, multiplication, and generalized operations in different settings.

### Totient Function

Definition and description of Euler's totient (phi) function.