  We describe a novel N-body code designed for simulations of the central
regions of galaxies containing massive black holes. The code incorporates
Mikkola's 'algorithmic' chain regularization scheme including post-Newtonian
terms up to PN2.5 order. Stars moving beyond the chain are advanced using a
fourth-order integrator with forces computed on a GRAPE board. Performance
tests confirm that the hybrid code achieves better energy conservation, in less
elapsed time, than the standard scheme and that it reproduces the orbits of
stars tightly bound to the black hole with high precision. The hybrid code is
applied to two sample problems: the effect of finite-N gravitational
fluctuations on the orbits of the S-stars; and inspiral of an intermediate-mass
black hole into the galactic center.
