stefangeens.com steangeens.com (which, incidentally, has a very elegant blog design – I really like his “sideblog” comments) – has a great entry on the most efficient way to crack The de Bruijn Code – that is, how to spin through all possible combinations of a four-digit number with as few keystrokes as possible (allowing for continuous recombination).
Now, if only the da Vinci Code had had just a little dusting of a bit of a shade of this way of thinking and writing…..