  In this paper we explicitly classify all modular invariant partition
functions for su(n) at level 2 and 3. Previously, these were known only for
level 1. The level 2 exceptionals exist at n=10, 16, and 28; the level 3
exceptionals exist at n=5, 9, and 21. One of these is new, but the others were
all anticipated by the "rank-level duality" relating su(n) level k and su(k)
level n. The main recent result which this paper rests on is the classification
of "ADE_7-type invariants".
