Clever Code Considered Harmful

I have personal proof of this.

I made a "clever" lisp (nth-fib x) and it has bugs I have never been able to get around. I keep it as a challenge. It has no loops, so it should be a whole lot faster than nearly every other version out there. It isn't and I don't know why. And it has a maximum nth that I also haven't been able to get around. Second example on this page: https://ksaj.inlisp.org. It's cool enough to look at and figure out that I posted it anyway, but broken so much that just about every non-clever version beats it to death.

Probably clever, but definitely harmful if ever used in production in all but the most basic / restricted situations.

I figure one day I might obfuscate it just to give it some reason to exist.