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Search: id:A020876
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| A020876 |
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Number of no-leaf edge-subgraphs in Moebius ladder M_n. |
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+0
7
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| 2, 5, 15, 50, 175, 625, 2250, 8125, 29375, 106250, 384375, 1390625, 5031250, 18203125, 65859375, 238281250, 862109375, 3119140625, 11285156250, 40830078125, 147724609375, 534472656250, 1933740234375
(list; graph; listen)
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OFFSET
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0,1
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REFERENCES
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J. P. McSorley, Counting structures in the Moebius ladder, Discrete Math., 184 (1998), 137-164.
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FORMULA
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((5+sqrt(5))/2)^n+((5-sqrt(5))/2)^n.
Let S(n, m)=sum(k=0, n, binomial(n, k)*fibonacci(m*k)), then for n>0 a(n)=S(2*n, 2)/S(n, 2) - Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 22 2003
a(n)= 5*a(n-1) -5*a(n-2). G.f.: (2-5*x)/(1-5*x+5*x^2). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 06 2010]
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PROGRAM
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sage: [lucas_number2(n, 5, 5) for n in xrange(0, 24)] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 08 2008
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CROSSREFS
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Sequence in context: A149946 A149947 A149948 this_sequence A093129 A149949 A149950
Adjacent sequences: A020873 A020874 A020875 this_sequence A020877 A020878 A020879
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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