Virial equation-of-state for the hard-disk fluid

Virial coefficients for the two-dimensional hard-disk fluid, when expressed in powers of density relative to maximum close packing, lead to an accurate closed equation-of-state for the equilibrium fluid, analogous to that recently found for hard spheres. The 2D series also converges for all densities up to a negative pole at close packing density. The virial pressure begins to deviate from the thermodynamic fluid in the approach to the ordering transition.