Local structure of graphs with λ=μ=2,a 2=4


Several properties of graphs with λ=μ=2,a 2=4 are studied. It is proved that such graphs are locally unions of triangles, hexagons or heptagons. As a consequence, a distance regular graph with intersection array (13,10,7;1,2,7) does not exist.

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    A. E. Brouwer, A. M. Cohen, andA. Neumaier:Distance-regular Graphs, Springer Verlag, Berlin, 1989.

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Coolsaet, K. Local structure of graphs with λ=μ=2,a 2=4. Combinatorica 15, 481–487 (1995). https://doi.org/10.1007/BF01192521

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Mathematics Subject Classification (1991)

  • 05 C 75