Be forewarned, however: Jim Kay's Marauder's Map illustration will make you want to sneak into Hogsmeade, even if you don't have mischief to manage. Isn't it gorgeous? I know I'm gushing here ...

Mathematicians have not yet succeeded in finding a formula for the number of different ways a road map ... left in the illustration below. There are 40 different ways that this “map” can ...