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%I #10 May 22 2024 15:15:01
%S 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
%N Number of nonisomorphic connected bipartite Y-graphs Y(n:i,j,k) on 8n vertices (or nodes) for 1<=i,j,k<=n.
%C 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.
%D I. Z. Bouwer, W. W. Chernoff, B. Monson, and Z. Starr (Editors), "Foster's Census", Charles Babbage Research Centre, Winnipeg, 1988.
%H J. D. Horton and I. Z. Bouwer, <a href="https://doi.org/10.1016/0095-8956(91)90057-Q">Symmetric Y-graphs and H-graphs</a>, J. Comb. Theory B 53 (1991) 114-129.
%e Y(4:1,1,1) is the smallest bipartite Y-graph.
%e Y(14:1,3,5) is the smallest bipartite symmetric (vertex- and edge-transitive) Y-graph.
%Y Cf. A112921, A112922, A112924.
%K nonn,more
%O 2,3
%A Marko Boben (Marko.Boben(AT)fmf.uni-lj.si), _Tomaz Pisanski_ and Arjana Zitnik (Arjana.Zitnik(AT)fmf.uni-lj.si), Oct 06 2005
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