Mathematical Aesthetics in a Beautiful Town

One of my works from the 2011 Bridges Mathematical Art Conference in Coimbra Portugal made it into the Notice of the AMS. Here's a link to the article and a screen shot of one of the pages.


xkcd puzzle

Here's a fun calculation from xkcd.com. Puzzle: why does this work? Can you find other numbers in which the same trick applies? Can you generalize?