A class number formula is a finite series giving exactly the class number of a ring. For a ring
of quadratic integers, the class number is denoted 
, where 
is the discriminant. A class number formula is known for the
full ring of cyclotomic integers, as well as for any subring of the cyclotomic integers.
This formula includes the quadratic case as well as many cubic and higher-order rings.
Class Number Formula
See also
Class Number, RingExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Class Number Formula." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ClassNumberFormula.html