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Search: id:A147859
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| A147859 |
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Chromatic polynomial pi_n(z) of the helm graph H_n evaluated at z=n. |
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+0
1
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| 0, 0, 0, 5832, 1228800, 384375000, 153080202240, 77461492681776, 48745516577587200, 37439062705187626320, 34519165560000000000000, 37661140521028611405206520, 48018043198541202818460549120, 70773783408692477397888505288296, 119443378434420330312430518726819840
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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The helm graph H_n is the graph obtained from an n-wheel graph by adjoining a pendant edge at each node of the cycle.
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REFERENCES
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Gallian, J. A. "Dynamic Survey DS6: Graph Labeling." Electronic J. Combinatorics, DS6, 1-58, 2007
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LINKS
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Eric W. Weisstein, Helm Graph
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FORMULA
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Pi_n(z) = z*((1-z)^n*(z-2)+(z-2)^n*(z-1)^n); a(n) = Pi_n(n).
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EXAMPLE
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a(3) = 3 * ((1 - 3)^3 * (3 - 2) + (3 - 2)^3 * (3 - 1)^3) = 0.
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MAPLE
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P := proc(n, z) z*((1-z)^n*(z-2)+(z-2)^n*(z-1)^n) ; end: A147859 := proc(n) P(n, n) ; end: for n from 1 to 15 do printf("%d, ", A147859(n)) ; od: # R. J. Mathar, Jan 22 2009
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CROSSREFS
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Sequence in context: A164649 A104284 A131494 this_sequence A035903 A114771 A013809
Adjacent sequences: A147856 A147857 A147858 this_sequence A147860 A147861 A147862
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Nov 16 2008
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EXTENSIONS
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Corrected parentheses, definition and values R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 22 2009
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