  We calculate the volume dependence of the ground-state energy of n identical
bosons with short-range repulsive interactions in a periodic spatial volume of
side L, up to and including terms of order 1/L^6. With this result, Lattice QCD
calculations of the ground-state energies of three or more pions will allow for
a systematic extraction of the three-pion interaction at this order in the
volume expansion.
