[VoidWhisperer]

Incase the author of the original article ends up reading this, is there any significance to the skipping of the 9th index after each face? (i.e. first face is 00-08, next one starts at 10 and goes to 18, then 20 to 28, etc)

A naive guess on my part is that doing it this way keeps the number in each specific spot of the 3x3 grid the same, X0 is the top left and X8 is the bottom right.

[Timwi]

I like your naive guess. Mine was that it's indexes into the input string and the skipped indexes are expected to be spaces.

Edit: another naive guess is that the numbers are actually in base-9 (to achieve the notational advantage you mentioned) and the author just forgot to mention that.