Hall-Janko Group
The Sporadic Group HJ, also denoted 
.
- Rhomboidal Dodecahedron
- Rhombus
- Rhumb Line
- Ribbon Knot
- Ribet's Theorem
- Riccati-Bessel Functions
- Riccati Differential Equation
- Ricci Curvature
- Ricci Tensor
- Rice Distribution
- Richardson Extrapolation
- Richardson's Theorem
- Richard's Paradox
- Ridders' Method
- Ridge
- Riemann-Christoffel Tensor
- Riemann Curve Theorem
- Riemann Differential Equation
- Riemann Function
- Riemann Hypothesis
- Riemannian Geometry
- Riemannian Geometry (Non-Euclidean)
- Riemannian Manifold
- Riemannian Metric
- Riemann Integral