prob023: magic hexagon

proposed by Toby Walsh
tw@cs.york.ac.uk

Results

The diameter 5 problem has (ignoring roations and reflections) an unique solution

10 12 16
13 4 2 19
15 8 5 7 3
14 6 1 17
9 11 18

There is also a (trivial) diameter 1 magic hexagon. These are the only two sizes of magic hexagon possible.

Eliminating symmetry is important. The diameter 5 problem has 12 symmetries (rotation, reflection, ...) which need to be considered.