The Paulus graphs are the 15 strongly regular graphs on 25 nodes with parameters (ν, k, λ, μ) = (25, 12, 5, 6) and the 10 strongly regular graphs on 26 nodes with parameters (26, 10, 3, 4). They are implemented in the Wolfram Language as GraphData[{Paulus, {n, i}}]. The (25, 15)-Paulus graph is isomorphic to the 25-Paley graph. The 25-node Paulus graphs are cospectral, as are the 26-node Paulus graphs, so none of these is determined by spectrum.

Chang graphs | cospectral graphs | determined by spectrum | Paley graph | Paulus-Rozenfeld-Thompson graph | strongly regular graph