Quadratic Chain

Quadrature

Quadrature of the Circle

Quadrichromatic Map

Quadrilateral

Quatrefoil

Quadrille

Quadruple Mill

Quaternary Order

Queen

Quickie

Quinary Order

Quincunx

Quintomino

Race

Railroad

Ramanujan Number

Random Game

Random Move

Random Number

Random Sequence

Rebus

Recreation

Recreational Mathematics

Recreational Problem

Rectangular Chessboard  

Rectangular Diagram

Rectangular Domino

Rectangular Grid

Rectangular Number  

Rectifiable Figure

Rectification

Rectification of the Circle

Rectilinear Jump

Rectilinear Lattice

Rectilinear Permutation

Recurrence

Red Donkey

Reduced Chessboard

Redundant Number

Reef Knot

Reentrant Circuit

Region

Relationship

Relatively Prime

Regression

Regularity

Regular Latin Square

Regular Polygon

Regular Polyhedron

Regular Tessellation

Relay

Rep-tile

Repdigit

Repunit

Remainders

Remainders Sharing

Remarquable Number

Reproducible Figure

Restitution

Reunion

Reversal

Reversed Magic Square

Reversed Number

Reversed Pair

Reversed Pyramid

Reversed Square 

Reversi

Reversible Digit

Reversible Figure

Reversible Magic Square

Reversible Number

Rhombicosidodecahedron

Rhombicuboctahedron

Rhombic Domino

Rhombohedron

Richard's Paradox

Riddle

Rook

Roman Numeral

Rose Window

Rotation 

Roulette

Rounds

Row

Roy Formula

Rubicube

Rubik's Cube

Rule of Three

Rules

Runner

Russell's Paradox

Russian Multiplication