I can't take credit for the solution I posted though.
I originally wrote a naive O(N^2) complexity solution (which was much shorter and was fine for the length of the input) I had this palindrome code in my 'toolbox' of code I've come across though, I'm afraid I don't know the orig author.
I just tweaked it as this is more in line with the type of example you're looking for.
Interesting, I'll have to go over your code fairly carefully, as I'm not familiar with every technique you're using here for performance.
I've since learned a good deal about Clojure and implemented an idiomatic (but probably less performant) version, for anyone interested in how short this can be:
