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An orientation of an undirected graph G is an assignment of exactly one direction to each of the edges of G. Only connected, bridgeless graphs can have a strong orientation ...

The square of a graph is defined as its second graph power. The square of any biconnected graph is Hamiltonian (Fleischner 1974, Skiena 1990, p. 231). Mukhopadhyay (1967) has ...

The union G=G_1 union G_2 of graphs G_1 and G_2 with disjoint point sets V_1 and V_2 and edge sets X_1 and X_2 is the graph with V=V_1 union V_2 and X=X_1 union X_2 (Harary ...

An (m+1)-dimensional subspace W of an (n+1)-dimensional vector space V can be specified by an (m+1)×(n+1) matrix whose rows are the coordinates of a basis of W. The set of ...

The great inverted snub icosidodecahedron is the uniform polyhedron with Maeder index 69 (Maeder 1997), Wenninger index 113 (Wenninger 1989), Coxeter index 73 (Coxeter et al. ...

The great rhombic triacontahedron, also called the great stellated triacontahedron, is the dual of great icosidodecahedron uniform polyhedron. It is a zonohedron and a ...

The great rhombidodecahedron is the uniform polyhedron with Maeder index 73 (Maeder 1997), Wenninger index 109 (Wenninger 1989), Coxeter index 89 (Coxeter et al. 1954), and ...

The great snub icosidodecahedron is the uniform polyhedron with Maeder index 57 (Maeder 1997), Wenninger index 116 (Wenninger 1989), Coxeter index 88 (Coxeter et al. 1954), ...

For any positive integer k, there exists a prime arithmetic progression of length k. The proof is an extension of Szemerédi's theorem.

Grelling's paradox, also known as the Grelling-Nelson paradox or heterological paradox, is a semantic paradox that arises by defining "heterological" to mean "a word which ...