Abstract
There is a unique distance regular graph with intersection array i (7, 6, 4, 4; 1, 1, 1, 6); it has 330 vertices, and its automorphism groupM 22.2 acts distance transitively. It does not have an antipodal 2-cover, but it has a unique antipodal 3-cover, and this latter graph has automorphism group 3.M 22.2 acting distance transitively. As a side result we show uniqueness of the strongly regular graph with parameters (v, k, λ, μ) = (231, 30, 9, 3) under the assumption that it is a gamma space with lines of size 3.
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Brouwer, A.E. Uniqueness and nonexistence of some graphs related toM 22 . Graphs and Combinatorics 2, 21–29 (1986). https://doi.org/10.1007/BF01788073
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DOI: https://doi.org/10.1007/BF01788073