  The small-scale structure problems of the universe can be solved by
self-interacting dark matter that becomes strongly interacting at low energies.
A particularly predictive model is resonant short-range self-interactions, with
a dark-matter mass of about 19 GeV and a large S-wave scattering length of
about 17 fm. Such a model makes definite predictions for the few-body physics
of weakly bound clusters of the dark-matter particles. We calculate the
production of two-body bound clusters by three-body recombination in the early
universe under the assumption that the dark matter particles are identical
bosons, which is the most favorable case for forming larger clusters. The
fraction of dark matter in the form of two-body bound clusters can increase by
as much as 4 orders of magnitude when the dark-matter temperature falls below
the binding energy, but its present value remains less than 10^(-6).
