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Search: id:A080838
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| A080838 |
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Orchard crossing number of complete bipartite graph K_{1,n}. |
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+0
2
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| 0, 0, 0, 2, 5, 12, 21, 36, 54, 80, 110, 150, 195, 252, 315, 392, 476, 576, 684, 810, 945, 1100, 1265, 1452, 1650, 1872, 2106, 2366, 2639, 2940, 3255, 3600, 3960, 4352, 4760, 5202, 5661, 6156, 6669, 7220, 7790, 8400, 9030, 9702, 10395, 11132, 11891
(list; graph; listen)
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OFFSET
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1,4
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LINKS
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D. Garber, [math/0303317] The Orchard crossing number of an abstract graph
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FORMULA
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n/16*(2n^2-8n+7+(-1)^n). G.f.: (x^5+2x^4)/(1-x)^4/(1+x)^2.
For n odd, a(n) = A060423(n). [From Gerald McGarvey (gerald.mcgarvey(AT)comcast.net), Sep 14 2008]
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PROGRAM
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(PARI) for(n=1, 100, print1(if(n%2, n*(n-1)*(n-3)/8, n*(n-2)^2/8)", "))
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CROSSREFS
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Sequence in context: A116728 A095306 A079648 this_sequence A106331 A116727 A116729
Adjacent sequences: A080835 A080836 A080837 this_sequence A080839 A080840 A080841
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KEYWORD
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nonn,easy
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AUTHOR
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Ralf Stephan (ralf(AT)ark.in-berlin.de), Mar 28 2003
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