Hall-Janko graph

In graph theory, the Hall-Janko graph is the unique strongly regular graph on 100 nodes, each of valency 36, such that every pair of neighboring nodes has 14 mutual neighbors and every pair of non-neighboring nodes has 12 mutual neighbors. It was constructed by Hall and D. Wales, and should probably therefore be called the Hall-Wales graph. Its group of automorphisms has a subgroup of index two which is the second Janko group, also known as the Hall-Janko group.

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