`1+2+3+4+... = -1/12`

wow. How is it possible?

that's called Ramanujan's sum.

you can learn it from the first 15 min of John Baez's lecture

this is quite amazing, touching on several things. See:

- Ramanujan summation
- 1 + 2 + 3 + 4 + …
- http://math.stackexchange.com/questions/39802/why-does-123-dots-1-over-12

on a separate note, the rest of Baez's video is also extremely interesting. It introduces you to concepts of string theory, quantum mechanics, spinor theory. See: John Baez on Octonion 📺