The -triangular honeycomb bishop graph (DeMaio and Tran 2013), called the hex bishop graph and denoted by Wagon (2014), is a graph consisting of vertices on a triangular honeycomb board with vertices along each side, where vertices are connected by an edge if they lie on the same or diagonal line of the chessboard (DeMaio and Tran 2013, Wagon 2014). The graphs for and 4 are illustrated above.
Note the moves considered in this definition differ from those allowed by the bishop piece in Gliński's hexagonal chess (Gliński 1973).
Rather surprisingly, the -triangular honeycomb bishop graph is isomorphic to the black bishop graph (Wagon 2014). Other special cases are summarized in the following table.
isomorphic graph | |
1 | singleton graph |
2 | path graph |
3 | cis-square with two triangles |
The -triangular honeycomb bishop graph has vertex count and edge count given by
(1)
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(2)
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(3)
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where is a binomial coefficient.
Triangular honeycomb bishop graphs are black bishop, class 1, claw-free, connected, line, nongeometric, perfect, quadratically embeddable, traceable, and weakly perfect.
Triangular honeycomb bishop graphs are implemented in the Wolfram Language as GraphData["TriangularHoneycombBishop", n].