  We formulate the two-point correlation function of primordial black holes
(PBHs) at their formation time, based on the functional integration approach
which has often been used in the context of halo clustering. We find that PBH
clustering on super-Hubble scales could never be induced in the case where the
initial primordial fluctuations are Gaussian, while it can be enhanced by the
so-called local-type trispectrum (four-point correlation function) of the
primordial curvature perturbations.
