It is no referring to any famous mathematical equation, it looks made up to me. Kind of like someone wanting to make an equation that looked aesthetically complex (that is complex to someone without a math background). Ironically, it looks like it is trying to do something with a set of a complex number, so it may be a joke or just coincidence.

Wikipedia's discussion page confirms it:

I think it's just gobbldegook. For example, j is supposed to be an element of the set of complex numbers or maybe complex vectors with i elements... but this is an infinite set, so you can't sum over it, only integrate... plus j is used as a subscript, which usually indicates an index, which ought to be integer. I'm not a mathematician though so I could be wrong and just not understand the notation... doubt it though. --Russell E 06:06, 11 May 2006 (UTC)

Some fellas on an Aphex Twin forum went to work on finding out what it was. One of 'em asked his mathematics teacher about it. The teacher said it was random bollocks. Later it was discovered that it is a line of code from a computer music program. It might have been csound or metasynth. Not sure. Wish I had a source for that, sorry.

No more Aphex Twin! EVIL, EVIIIIIIIL!

He's not evil! Why, look at the cute teddy bears...

does it mean that pi is exactly three?