[en] The position of the pole in k cotdelta, for doublet s-wave n-d scattering, and its residue are shown to be correlated with the doublet scattering length. An approximate, analytic solution of the N/D equations of Barton and Phillips indicates a linear dependence on the doublet scattering length for the pole position, and a quadratic dependence for the residue. These relationships are tested by means of exact numerical solutions of N/D equations and three-particle equations, with separable two-particle interactions, and found to be qualitatively correct. The approximate, analytic solution of the N/D equations leads to a formula for k cotdelta, which is of the same form as the phenomenological formula used previously by other authors. A formalism is presented which makes it possible to parametrize the effect of the omitted portion of the left hand cut in an N/D calculation