Gregory Number
A number
where
is an Integer or Rational Number, 
is the Inverse Tangent, and 
is the Inverse Cotangent. Gregory numbers arise in the determination of Machin-Like Formulas.Every Gregory number 
can be expressed uniquely as a sum of 
s where the 
s are Stérmer Numbers.
References
Conway, J. H. and Guy, R. K. ``Gregory's Numbers'' In The Book of Numbers. New York: Springer-Verlag, pp. 241-242, 1996.
- Idempotent
- Identity
- Identity Element
- Identity Function
- Identity Map
- Identity Matrix
- Identity Operator
- Idoneal Number
- Iff
- Ill-Conditioned
- Illumination Problem
- Illusion
- Image
- Imaginary Identity
- Imaginary Number
- Imaginary Part
- Imaginary Point
- Imaginary Quadratic Field
- Immanant
- Immersed Minimal Surface
- Immersion
- Impartial Game
- Implicit Function
- Implicit Function Theorem
- Implies