I'm trying to prove through induction. (and for 5 in but that's for later)

Done the base case which simplifies to 2

Assume for evaluates to

Inductive prove for evaluates to

But I'm guessing you have to add and minus some value before to incorporate the assumption so I'm guessing we do something here:

Don't know what exactly, pointers?

Sorry about the mundane question. I'm not wired to think the 2 steps ahead for proofs.