This is intended to be an undergraduate textbook presenting a somewhat geometrically-flavored introduction to elementary number theory.

Summary:

• Chapter 0. Preview
• Chapter 1. The Farey Diagram
• Chapter 2. Continued Fractions
• Chapter 3. Linear Fractional Transformations
• Chapter 4. Quadratic Forms
• Chapter 5. Classification of Quadratic Forms
• Chapter 6. Representations by Quadratic Forms
• Chapter 7. Quadratic Fields