Wells graph
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The Wells graph is the unique distance-regular graph with intersection array { 5 , 4 , 1 , 1 ; 1 , 1 , 4 , 5 } . {\displaystyle \{5,4,1,1;1,1,4,5\}.}
Its spectrum is 5 1 5 8 1 10 ( − 5 ) 8 ( − 3 ) 5 {\displaystyle 5^{1}{\sqrt {5}}^{8}1^{10}(-{\sqrt {5}})^{8}(-3)^{5}}. Its queue number is 3 and an upper bound on its book thickness is 5.