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- Kirby Calculus
- Kirby's List
- Kirkman's Schoolgirl Problem
- Kirkman Triple System
- Kissing Circles Problem
- Kissing Number
- Kiss Surface
- Kite
- Klarner-Rado Sequence
- Klarner's Theorem
- Klein-Beltrami Model
- Klein Bottle
- Klein Four-Group
- Klein-Gordon Equation
- Kleinian Group
- Klein Quartic
- Klein's Absolute Invariant
- Klein's Equation
- Klein's Theorem
- Kloosterman's Sum
- k-Matrix
- Knapsack Problem
- Kneser-Sommerfeld Formula
- Knights of the Round Table
- Knights Problem