Prime Knot
A Knot other than the Unknot which cannot be expressed as a sum of two other Knots, neither ofwhich is unknotted. A Knot which is not prime is called a Composite Knot. It is often possible to combine twoprime knots to create two different Composite Knots, depending on the orientation of the two.
There is no known Formula for giving the number of distinct prime knots as a function of the number of crossings. For thefirst few 
crossings, the numbers of prime knots are 0, 0, 1, 2, 3, 7, 21, 49, 165, 552, 2176, 9988, ... (Sloane's A002863).
References
Sloane, N. J. A. SequenceA002863/M0851in ``An On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html and extended entry inSloane, N. J. A. and Plouffe, S.The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.
- Super-Poulet Number
- Superregular Graph
- Superscript
- Superset
- Supplementary Angle
- Support
- Support Function
- Supremum
- Supremum Limit
- Surd
- Surface
- Surface Area
- Surface Integral
- Surface of Revolution
- Surface of Section
- Surface Parameterization
- Surgery
- Surjection
- Surjective
- Surprise Examination Paradox
- Surreal Number
- Surrogate
- Surveying Problems
- Survivorship Curve
- Suslin's Theorem