%I A112923
%S A112923 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 A112923 Number of nonisomorphic connected bipartite Y-graphs Y(n:i,j,k) on 8n 
               vertices (or nodes) for 1<=i,j,k<=n.
%C A112923 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 A112923 I. Z. Bouwer, W. W. Chernoff, B. Monson and Z. Starr (Eds.), "Foster's 
               Census", Charles Babbage Research Centre, Winnipeg, 1988.
%D A112923 J. D. Horton and I. Z. Bouwer, Symmetric Y-graphs and H-graphs, J. Comb. 
               Theory B 53 (1991) 114-129
%e A112923 Y(4:1,1,1) is the smallest bipartite Y-graph.
%e A112923 Y(14:1,3,5) is the smallest bipartite symmetric (vertex- and edge-transitive) 
               Y-graph.
%Y A112923 Cf. A112921, A112922, A112924.
%Y A112923 Sequence in context: A068465 A025498 A128971 this_sequence A098366 A162200 
               A000019
%Y A112923 Adjacent sequences: A112920 A112921 A112922 this_sequence A112924 A112925 
               A112926
%K A112923 nonn
%O A112923 2,3
%A A112923 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