Pair Sum
Given an Amicable Pair 
, the quantity
is called the pair sum, where
is the Divisor Function and 
is the Restricted Divisor Function. See also Amicable Pair- Sinusoidal Spiral Pedal Curve
- Sister Celine's Method
- Site Percolation
- Siteswap
- Six-Color Theorem
- Skein Relationship
- Skeleton
- Skeleton Division
- Skew Conic
- Skewes Number
- Skew Field
- Skew Lines
- Skewness
- Skew Polyomino
- Skew Quadrilateral
- Skew Symmetric Matrix
- Sklar's Theorem
- Skolem-Mahler-Lerch Theorem
- Skolem Paradox
- Skolem Sequence
- Slant Height
- Slice Knot
- Slide Move
- Slide Rule
- Slightly Defective Number