Took me way too long to get that

The infinite sum of all the natural numbers 1+2+3+… is a divergent series. But it can also be shown to be equivalent to -1/12. This result is actually used in quantum field theory.

I found it on mastodon. Searching hashtag #LK99

This seems like a good page to keep track of the replication attempts. https://forums.spacebattles.com/threads/claims-of-room-temperature-and-ambient-pressure-superconductor.1106083/page-21