  The O(n) vector model with logarithmic action on a lattice of coordination 3
is related to a gas of self-avoiding loops on the lattice. This formulation
allows for analytical continuation in n: critical behaviour is found in the
real interval [-2,2]. The solution of the model on random planar lattices,
recovered by random matrices, also involves an analytic continuation in the
number n of auxiliary matrices. Here we show that, in the two cases n=-1, -2, a
combinatorial reformulation of the loop gas problem allows to achieve the
random matrix solution with no need of this analytical continuation.
