Here is a "problem cluster" from our overlapping square region network.
You can see that the center cluster has greatly varying digits linked 
together without obvious reason.

            _|-> 4
           |-| |   |-| |-> 4
             | | |-| |-> 4
             | | | |-> 4
             |-| |        _|-> 3
               | |       | |_|-> 5
               | |     |-|   |_|-> 6
               | |     | |     |-> 8
               | |   |-| |-> 9
               | |   | |  _|-> 3
               |-|   | | | |_|-> 5
                 | |-| |-|   |-> 8
                 | | |   |_|-> 9
                 | | |     |-> 7
                 | | |_|-> 4
                 | |   |-> 4
                 | |    _|-> 1
                 | | |-| |-> 1
                 | | | |_|-> 1
                 |-| |   |-> 1