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Search: id:A112921
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| A112921 |
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Number of nonisomorphic Y-graphs Y(n:i,j,k) on 4n vertices (or nodes) for 1<=i,j,k<n/2. |
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5
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| 1, 1, 2, 4, 4, 6, 8, 10, 7, 24, 10, 20, 26, 26, 15, 44, 19, 54, 44, 44, 26, 102, 38, 62, 57, 96, 40, 164, 46, 104, 91, 102, 91, 213, 64, 128, 124, 222, 77, 290, 85, 212, 200, 184, 100, 388, 128, 268, 199, 292, 126
(list; graph; listen)
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OFFSET
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3,3
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COMMENT
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A Y-graph Y(n:i,j,k) has 4n vertices arranged in four segments of n vertices. Let the vertices be v_{x,y} for x=0,1,2,3 and y in the integers modulo n. The edges are v_{1,y}v_{1,y+i}, v_{2,y}v_{2,y+j}, v_{2,y}v_{2,y+k} and v_{0,y}v_{x,y}, where y=0,1,...,n-1 and x=1,2,3 and the subscript addition is performed modulo n.
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REFERENCES
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I. Z. Bouwer, W. W. Chernoff, B. Monson, and Z. Starr (Eds.), "Foster's Census", Charles Babbage Research Centre, Winnipeg, 1988.
J. D. Horton and I. Z. Bouwer, Symmetric Y-graphs and H-graphs, J. Comb. Theory B 53 (1991) 114-129
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EXAMPLE
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Y(7:1,2,3) is the Coxeter graph, the only (connected) symmetric (vertex- and edge-tansitive) Y-graph of girth 7 or less.
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CROSSREFS
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Cf. A112922, A112923, A112924, A112921, A107452.
Adjacent sequences: A112918 A112919 A112920 this_sequence A112922 A112923 A112924
Sequence in context: A063224 A023847 A000061 this_sequence A008133 A022471 A081238
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KEYWORD
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nonn
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AUTHOR
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Marko Boben (Marko.Boben(AT)fmf.uni-lj.si), Tomaz Pisanski (Tomaz.Pisanski(AT)fmf.uni-lj.si) and Arjana Zitnik (Arjana.Zitnik(AT)fmf.uni-lj.si), Oct 06 2005
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