One of the features I started using extensively this year is a threading macro. Also, I wanted to give an honorable mention to some higher-order functions we have out of the box from Racket.
Anyways, function memoization, amiright? "Top-down" dynamic programming. Before attempting to calculate the function result for a particular set of parameters, we look up the table first to avoid doing the same work twice.
In your first post, you're expected to uncover the motivation behind this whole project and justify its very existence. I'll give it a try — but I won't try too hard, that's for sure.