Formulas
- Rook polynomial
- Rota–Baxter algebra
- Routh–Hurwitz theorem
- Rudin–Shapiro sequence
- Runge's phenomenon
- Runge–Kutta–Fehlberg method
- Running angle
- Russo–Dye theorem
- Trigonometric moment problem
- Weakly harmonic function
- Schreier vector
- The Housekeeper and the Professor
- Topological ring
- The Whetstone of Witte
- Thue equation