Klein's Absolute Invariant
(Cohn 1994), where
is the Nome, 
is the Elliptic Lambda Function
is a Theta Function, and the 
are Ramanujan-Eisenstein Series. 
is Gamma-Modular.See also Elliptic Lambda Function, j-Function, Pi, Ramanujan-Eisenstein Series, Theta Function
References
Borwein, J. M. and Borwein, P. B. Pi & the AGM: A Study in Analytic Number Theory and Computational Complexity. New York: Wiley, pp. 115 and 179, 1987. Cohn, H. Introduction to the Construction of Class Fields. New York: Dover, p. 73, 1994.
Weisstein, E. W. ``j-Function.'' Mathematica notebook jFunction.m.
- Algebraic Tangle
- Algebraic Topology
- Algebraic Variety
- Algebroidal Function
- Algorithm
- Algorithmic Complexity
- Alhazen's Billiard Problem
- Alhazen's Problem
- Aliasing
- Aliquant Divisor
- Aliquot Cycle
- Aliquot Divisor
- Aliquot Sequence
- Alladi-Grinstead Constant
- Allais Paradox
- Allegory
- Allometric
- All-Poles Model
- Almost All
- Almost Alternating Knot
- Almost Alternating Link
- Almost Everywhere
- Almost Integer
- Almost Perfect Number
- Almost Prime