>>297 追加

なんか、全部
en.wikipedia. j-invariant に書いてあった
読めてなかった・・　 ；ｐ）
引用しておく （＾＾

(参考)
https://en.wikipedia.org/wiki/J-invariant
j-invariant
In mathematics, Felix Klein's j-invariant or j function is a modular function of weight zero for the special linear group
SL(2,Z) defined on the upper half-plane of complex numbers. It is the unique such function that is holomorphic away from a simple pole at the cusp such that
j(e2πi/3)=0,j(i)=1728=123.
Rational functions of j are modular, and in fact give all modular functions of weight 0. Classically,
the j-invariant was studied as a parameterization of elliptic curves over C, but it also has surprising connections to the symmetries of the Monster group (this connection is referred to as monstrous moonshine).

Alternate expressions
where x = λ(1 − λ) and λ is the modular lambda function （モジュラーλ函数ご登場）
（表式略）

Algebraic definition
（3次式が出てくるが略す。やっぱ 3次式が主じゃね？　（＾＾）
We also have the discriminant （判別式）
Δ= 略す