Wikipedia:Reference desk/Archives/Mathematics/2011 June 8

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June 8

Example of a graph

Can someone please give me an example of a k-regular connected graph G, (k>2) which has order 4 or more and contains a triangle but no square?-Shahab (talk) 06:14, 8 June 2011 (UTC)

Markström graph

I have an example of order 10, but I'm going to have to draw it. I did a quick search on Commons to see if there was already an image of it there, and I found the Markström graph (see right), which is another example. —Bkell (talk) 07:20, 8 June 2011 (UTC)

The Dürer graph is also an example. —Bkell (talk) 07:22, 8 June 2011 (UTC)

And Tietze's graph. (I'm running through the list at commons:Graphs in graph theory, by the way.) —Bkell (talk) 07:25, 8 June 2011 (UTC)

Three of the truncated Platonic solids, too. The truncated tetrahedron is pretty close to the example I came up with; here's a poor attempt to draw my example (the O's are the vertices):

   O---------O
  / \       / \
 /   \     /   \
O-----O   O-----O
 \     \ /     /
  \     O     /
   \    |    /
    \   O   /
     \ / \ /
      O---O

—Bkell (talk) 07:40, 8 June 2011 (UTC)