It has occurred to me that Sudoku (playing, studying) involves a large number of concepts from combinatorics.

Therefore I thought it might be nice to write up some elementary "essays" on combintorial topics that used Sudoku as a running example.

I have done an example of such an essay based on the concept of SYMMETRY...

http://www.csse.uwa.edu.au/~gordon/sudoku/sudoku-symmetry.pdf

The idea here is to explain the FORMAL mathematics (at a beginner's level) underlying the concepts of a symmetric puzzle. This sort of complements the various informal descriptions (by Tso in particular) of symmetries.

Those familiar with group theory and combinatorics will recognize the basic arguments as common to every beginning text book known to man, but hopefully the Sudoku twist adds some extra interest.

Comments and feedback welcomed..

Gordon