The Perkel graph is a weakly regular graph on 57 vertices and 171 edges, shown above in several embeddings. It is the unique
distance-regular graph with intersection
array
(Coolsaet and Degraer 2005, Brouwer). The Perkel graph is also distance-transitive.
It is also the skeleton of the 57-cell.
It has graph spectrum .
It is implemented in the Wolfram Language as GraphData["PerkelGraph"].