1+2+3+…=-1/12, but not really

These people would have completely failed the calculus classes I took in undergrad. Why 1+2+3+…=-1/12.

To see why what they do is mathematical foolishness, see for example Riemann series theorem.

And interestingly enough there is some real math going on… See Ramanujan summation.

…which in no way implies the claim.