Clear out textboxes using recursion and LINQ; use VB literals to transform an XML document; and eliminate an annoying artifact of VB internals.

Wait, you want to use factorials or you want to use recursion? A factorial-based approach would involve mapping 0.. (n! - 1) to different permutations.

Recursion is (in many, but not all) languages slightly slower, and it does have some dangers (smashing the stack), but used properly it's a completely legitimate, valuable tool for production code.