Euler Characteristic
Let a closed surface have Genus 
. Then the Polyhedral Formula becomes thePoincaré Formula
 | (1) |
is the Euler characteristic, sometimes also known as the Euler-PoincaréCharacteristic. In terms of the Integral Curvature of the surface 
, | (2) |
 | (3) |
is the 
th Betti Number of the space.See also Chromatic Number, Map Coloring- Restricted Growth Function
- Restricted Growth String
- Resultant
- Retardance
- Reuleaux Polygon
- Reuleaux Triangle
- Reversal
- Reverse Greedy Algorithm
- Reverse-Then-Add Sequence
- Reversion of Series
- Reznik's Identity
- Rhodonea
- Rhomb
- Rhombic Dodecahedral Number
- Rhombic Dodecahedron
- Rhombic Icosahedron
- Rhombicosacron
- Rhombicosahedron
- Rhombicosidodecahedron
- Rhombic Polyhedron
- Rhombic Triacontahedron
- Rhombicuboctahedron
- Rhombidodecadodecahedron
- Rhombihexacron
- Rhombihexahedron