  Hexagonal polyominoes are polyominoes on the honeycomb lattice. We enumerate
the symmetry classes of convex hexagonal polyominoes. Here convexity is to be
understood as convexity along the three main column directions. We deduce the
generating series of free (i.e. up to reflection and rotation) and of
asymmetric convex hexagonal polyominoes, according to area and half-perimeter.
We give explicit formulas or implicit functional equations for the generating
series, which are convenient for computer algebra.
