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# Pappus graph

The Pappus graph Γ is the bipartite incidence graph of the
9 points and 9 lines of the affine plane AG(2,3) minus
a parallel class.
It is cubic, of girth 6.
It is the unique distance-regular graph with intersection array
{3,2,2,1; 1,1,2,3}.

## Group

Γ is distance transitive with group 3^{2}:3:2:2:2 of order 216
with point stabilizer D_{12}.

## Spectrum

Γ has spectrum ±3, (±√3)^{6}, 0^{4}
and is uniquely determined by its spectrum.