<Verb>DendrogramMat(A,t,s):: Mat, Rat, Int --> List</Verb><P/>
<P/> Inputs an <M>n\times n</M>
symmetric matrix <M>A</M> over the rationals, a rational
<M>t \ge 0</M> and an integer <M>s \ge 1</M>.
A list <M>[v_1, \ldots, v_{t+1}]</M> is returned with each <M>v_k</M> a
list of positive integers.
Let <M>t_k = (k-1)s</M>.
Let <M>G(A,t_k)</M> denote the graph with vertices
<M>1, \ldots, n</M> and with distinct vertices <M>i</M> and <M>j</M>
connected by an edge when the <M>(i,j)</M> entry of <M>A</M> is <M>\le t_k</M>.
The <M>i</M>-th path component of <M>G(A,t_k)</M> is included
in the <M>v_k[i]</M>-th path component of <M>G(A,t_{k+1})</M>. This defines the integer vector <M>v_k</M>.
The vector <M>v_k</M> has length equal to the number of path components of
<M>G(A,t_k)</M>.
