Formulas
- Coastline paradox
- Coherence condition
- Coins in a fountain
- Collatz conjecture
- Thom conjecture
- Tight closure
- Alexander Arhangelskii
- Time-scale calculus
- Alexander duality
- Alexandroff extension
- Topological combinatorics
- Trivial group
- Nottingham group
- Novikov's compact leaf theorem
- Primitive recursive set function