  The discrete vortex lattices in a ferromagnet/superconductor bilayer are
studied when the ferromagnet has periodic stripe domains with an out-of-plane
magnetization. The vortices are assumed to be situated periodically on chains
in the stripe domains. Only up to two vortex chains per domain configurations
are considered. When the domain period is fixed, the threshold magnetization is
calculated at which the transition from the Meissner state to the mixed state
occurs. When the domain period is not fixed, the equilibrium domain size and
vortex positions are calculated, depending on the domain's magnetization and
the domain wall energy. In equilibrium, the vortices in the neighbor domains
are half-way shifted, while they are next to each other in the same domain.
