Dirichlet Structure Constant
where
is the Fundamental Unit and 
is the number of substitutions which leave the binary quadraticform unchanged
See also Class Number, Dirichlet L-Series
References
Weisstein, E. W. ``Class Numbers.'' Mathematica notebook ClassNumbers.m.
- Smale Horseshoe Map
- Small Cubicuboctahedron
- Small Ditrigonal Dodecacronic Hexecontahedron
- Small Ditrigonal Dodecicosidodecahedron
- Small Ditrigonal Icosidodecahedron
- Small Dodecacronic Hexecontahedron
- Small Dodecahemicosacron
- Small Dodecahemicosahedron
- Small Dodecahemidodecacron
- Small Dodecahemidodecahedron
- Small Dodecicosacron
- Small Dodecicosahedron
- Small Dodecicosidodecahedron
- Small Hexacronic Icositetrahedron
- Small Hexagonal Hexecontahedron
- Small Hexagrammic Hexecontahedron
- Small Icosacronic Hexecontahedron
- Small Icosicosidodecahedron
- Small Icosihemidodecacron
- Small Icosihemidodecahedron
- Small Inverted Retrosnub Icosicosidodecahedron
- Axial Vector
- Axiom
- Axiom A Diffeomorphism
- Axiom A Flow