  We discuss the dynamics of a Bose-Einstein condensate initially loaded into
every third site of an optical lattice using a description based upon the
discrete nonlinear Schrodinger equation. An analytic solution is developed for
the case of a periodic initial condition and is compared with numerical
simulations for more general initial configurations.
  We show that mean field effects in this system can cause macroscopic quantum
self-trapping, a phenomenon already predicted for double well systems. In the
presence of a uniform external potential, the atoms exhibit generalized Bloch
oscillations which can be interpreted in terms of the interference of three
different Bloch states. We also discuss how the momentum distribution of the
system can be used as experimental signature of the macroscopic self trapping
effect.
