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From: ljdickey@watmath.UUCP
Newsgroups: net.math
Subject: stuff
Message-ID: <5376@watmath.UUCP>
Date: Fri, 10-Jun-83 16:16:05 EDT
Article-I.D.: watmath.5376
Posted: Fri Jun 10 16:16:05 1983
Date-Received: Sat, 11-Jun-83 20:11:35 EDT
Lines: 18

OK,  Dean Hoffman has solved your puzzle.
Here are two graphs, each with 9 vertices.
That means there are 36 pairs of vertices.
Each of them has 12 pairs with distance 2 apart, and
each of them has 24 pairs with distance 4 apart.

              o                                   o o o
              |                                    \|/
              o                                  o--o--o
              |                                     |
    o--o------o------o--o                 o--o------o------o--o
      /|\           /|\                      |             |
     o o o         o o o                     o             o

Lee Dickey
Department of Pure Mathematics
University of Waterloo
...!decvax!watmath!ljdickey