Kollros' Theorem
For every ring containing 
Spheres, there exists a ring of 
Spheres, each touching each of the Spheres, where
The Hexlet is a special case with
.See also Hexlet, Sphere
References
Honsberger, R. Mathematical Gems II. Washington, DC: Math. Assoc. Amer., p. 50, 1976.
- Separating Edge
- Separating Family
- Separation
- Separation of Variables
- Separation Theorem
- Separatrix
- Septendecillion
- Septillion
- Sequence
- Sequency
- Sequency Function
- Sequential Graph
- Series
- Series Expansion
- Series Inversion
- Series Multisection
- Series Reversion
- Serpentine Curve
- Serret-Frenet Formulas
- Set
- Set Difference
- Set Partition
- Set Theory
- Sexagesimal
- Sexdecillion