@H.PWiz Sure seems like it should be impossible. Both the OEIS definition and Dennis's are recursive. Did you have an idea as to why it might be possible?

Incidentally, I transcribed Grimy's optimizations to my abundant numbers regex into git, up to the point that it started to get difficult to prove that the optimizations were correct, and at that point left it for later.

A subset of the ones that reduced it from 504 to 392 chars reduce the fast version from 537 to 455 chars (only one out of the twelve of them was not applicable).