User:David Eppstein/Gallery

Divisibility of regular numbers.

Series-parallel graph.

Split graph.

Convex shelling.

Three views of an antimatroid.

The Nagel point of a triangle.

Square pyramidal number.

The Philo line and its application to doubling the cube.

Rational approximations to the octagon from Pell numbers.

Integer right triangles with nearly-equal legs from Pell numbers.

Partition of the torus into seven mutually adjacent regions, for Heawood conjecture.

Graphical demonstration of a solution to Znám's problem.

Graphical demonstration that 1 = 1/2 + 1/3 + 1/7 + 1/43 + ...; see Sylvester's sequence.

The rooted product of graphs.

The lexicographic product of graphs.

The tensor product of graphs.

The cartesian product of graphs.

A switch in a train track, and the corresponding portion of a lamination.

A train track on a triple torus

Orthogonal convex hull and tight span

The Paley graph of order 9 as a perfect graph

The de Bruijn graph as a line graph

Beineke's nine forbidden line graphs

The Grötzsch graph.

The Grötzsch graph as the Mycielskian of a 5-cycle graph.

The Szilassi polyhedron. From the junkyard.

Point sets with fewer than n/2 ordinary lines

König's theorem (graph theory) proof

König's theorem (graph theory) example

The lattice of subgroups of Dih₄, drawn as a Hasse diagram

A concept lattice, drawn as a Hasse diagram

No-three-in-line problem

An aperiodic graph

A graph that is not aperiodic as all cycles are divisible by three

Three-dimensional binary De Bruijn graph

Thue number of the 5-cycle is four

Happy Ending problem, quadrilaterals in five point sets

Happy Ending problem, eight points with no pentagon

Möbius ladder, two views of M₁₆

Erdős–Szekeres theorem, geometric interpretation as monotone path

Paley graph, of order 13, as a circulant

Wheel graphs with 4 to 9 vertices

Turán graph T(13,4)

The Petersen graph as a Moore graph

Desargues' configuration as two mutually inscribed pentagons

Complete quadrangle and dual complete quadrilateral

Hadwiger–Nelson problem: 7-coloring of the plane and 4-chromatic unit distance graph. From the junkyard.

Unit disk graph

Erdős–Gyárfás conjecture, Markström's 4- and 8-cycle-free graph

Strict weak ordering, the 13 orders on 3 elements

Dilworth's theorem, transformation from chain decomposition to bipartite matching

Day & Night, Bell's p256 butterfly gun

Heesch's problem, Amman's dented hexagon. From the junkyard.

Fáry's theorem, induction step of proof