This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A112921 #13 May 22 2024 15:13:09
%S A112921 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,
%T A112921 96,40,164,46,104,91,102,91,213,64,128,124,222,77,290,85,212,200,184,
%U A112921 100,388,128,268,199,292,126
%N A112921 Number of nonisomorphic Y-graphs Y(n:i,j,k) on 4n vertices (or nodes) for 1<=i,j,k<n/2.
%C A112921 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 A112921 I. Z. Bouwer, W. W. Chernoff, B. Monson, and Z. Starr (Editors), "Foster's Census", Charles Babbage Research Centre, Winnipeg, 1988.
%H A112921 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 A112921 Y(7:1,2,3) is the Coxeter graph, the only (connected) symmetric (vertex- and edge-transitive) Y-graph of girth 7 or less.
%Y A112921 Cf. A112922, A112923, A112924, A112921, A107452.
%K A112921 nonn,more
%O A112921 3,3
%A A112921 Marko Boben (Marko.Boben(AT)fmf.uni-lj.si), _Tomaz Pisanski_ and Arjana Zitnik (Arjana.Zitnik(AT)fmf.uni-lj.si), Oct 06 2005