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Search: id:A112923
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| A112923 |
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Number of nonisomorphic connected bipartite Y-graphs Y(n:i,j,k) on 8n vertices (or nodes) for 1<=i,j,k<=n. |
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4
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| 1, 1, 2, 2, 5, 4, 5, 7, 9, 7, 14, 10, 15, 23, 15, 15, 27, 19, 28, 39, 29, 26, 45, 36, 39
(list; graph; listen)
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OFFSET
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2,3
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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(4:1,1,1) is the smallest bipartite Y-graph.
Y(14:1,3,5) is the smallest bipartite symmetric (vertex- and edge-transitive) Y-graph.
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CROSSREFS
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Cf. A112921, A112922, A112924.
Sequence in context: A068465 A025498 A128971 this_sequence A098366 A162200 A000019
Adjacent sequences: A112920 A112921 A112922 this_sequence A112924 A112925 A112926
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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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