This is the answer to the divergent series problem I posed yesterday.

Caveat: this is not a sum in the traditional way. It's basically a "trick" that is sometimes used in physics to get rid of annoying infinities... like we know that the energy should not be infinite, so we cancel out one infinite sum with another infinite sum to find a solution that works in the finite regime. I think they made a follow up video to better contextualize when such renormalization is a valid thing to do.