Circulant graph
In graph theory, a circulant graph is an undirected graph that has a cyclic group of symmetries that includes a symmetry taking any vertex to any other vertex.
Equivalent definitions
Circulant graphs can be described in several equivalent ways:
The automorphism group of the graph includes a cyclic subgroup that acts transitively on the graph's vertices.
The graph has an adjacency matrix that is a circulant matrix.
The n vertices of the graph can be numbered from 0 to n − 1 in such a way that, if some two vertices numbered x and (x +d) mod n are adjacent, then every two vertices numbered z and (z +d) mod n are adjacent.
The graph can be drawn (possibly with crossings) so that its vertices lie on the corners of a regular polygon, and every rotational symmetry of the polygon is also a symmetry of the drawing.
The graph is a Cayley graph of a cyclic group.
Examples
Every cycle graph is a circulant graph, as is every crown graph with 2 modulo 4 vertices.
The Paley graphs of order n (where n is a prime number congruent to 1 modulo 4) is a graph in which the vertices are the numbers from 0 to n − 1 and two vertices are adjacent if their difference is a quadratic residue modulo n. Since the presence or absence of an edge depends only on the difference modulo n of two vertex numbers, any Paley graph is a circulant graph.