Interesting indeed. But weird that he uses obfuscated code when doing a piece of explaining how it's done. Or do people actually write for loops like those? :P
This is basically the a C equivalent of a JAPH. A JAPH is a usually short bit of perl code that prints "Just Another Perl Hacker", but it isn't obvious that that's what it does. Trying to figure out how it works without cheating is part of the fun.