  Third and higher order quantum virial coefficients require the solution of
the corresponding quantum many-body problem. Nevertheless, in an earlier paper
(Phys. Rev. Lett. 108, 260402 (2012)) we proposed that the higher-order cluster
integrals of a dilute unitary fermionic gas may be approximated in terms of the
two-body cluster, together with an appropriate suppression factor. Although not
exact, this ansatz gave a fair agreement up to fugacity z=6 with the
experimentally obtained equation of state. The objective of the present note is
to give some physical arguments in favor of this ansatz.
