  In recent work the author presented a formal expansion for lambda_d
associated to the dimer problem on a d-dimensional rectangular lattice.
Expressed in terms of d it yielded a presumed asymptotic expansion for lambda_d
in inverse powers of d. We also considered an expansion in powers of x, a
formal variable ultimately set equal to 1. We believe this series has better
asymptotic properties than the expansion in inverse powers of d. We discuss
this, and apply the same method to the two-dimensional triangular and hexagonal
lattices. Viewed as a test of the x-expansion the results on those two lattices
are satisfactory, if not thoroughly convincing.
