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Let a simple graph have vertices, chromatic polynomial , and chromatic number . Then can be written as
where and is a falling factorial, and the polynomial
is known as the -polynomial (Frucht and Giudici 1983; Li et al. 1987; Read and Wilson 1998, p. 265).
-polynomials for a number of simple graphs are summarized in the following table.
graph | |
claw graph | |
complete graph | 1 |
cubical graph | |
cycle graph | |
octahedral graph | |
path graph | |
pentatope graph | 1 |
square graph | |
star graph | |
star graph | |
tetrahedral graph | 1 |
triangle graph | 1 |
wheel graph | |
wheel graph |
Frucht, R. W. and Giudici, R. E. "Some Chromatically Unique Graphs with Seven Points." Ars Combin. A 16, 161-172, 1983.
Korfhage, R. R. "-Polynomials and Graph Coloring." J. Combin. Th. Ser. B 24, 137-153, 1978.
Li, N.-Z.; Whitehead, E. G. Jr.; and Xu, S.-J. "Classification of Chromatically Unique Graphs Having Quadratic -Polynomials." J. Graph Th. 11, 169-176, 1987.
Read, R. C. and Wilson, R. J. An Atlas of Graphs. Oxford, England: Oxford University Press, p. 265, 1998.
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