This is an antipodal 3-cover of the Brouwer–Haemers graph, and an induced subgraph of Soicher's second graph.

Number of vertices: | $243$ |

Diameter: | $4$ |

Intersection array: | $\{20,18,4,1;1,2,18,20\}$ |

Spectrum: | $20^1 5^{72} 2^{60} (-4)^{90} (-7)^{20}$ |

Automorphism group: | $3^5:(2\times M_{10})$ |

Distance-transitive: | $\text{Yes}$ |

Antipodal |

- $\text{Adjacency matrix}$
- $\text{Adjacency matrix in GAP format}$
- $\text{Adjacency matrix in CSV format}$
- $\text{Graph in GRAPE format}$

- R.F. Bailey and D.R. Hawtin, On the 486-vertex distance-regular graphs of Koolen--Riebeek and Soicher, preprint, 2019 (arXiv:1908.07104).