The Number -1/12...One More Time

Here's a followup video by Numberphile about their earlier demonstration that, in some sense

1 + 2 + 3 + 4 + 5 + .... = -1/12
The mathematician speaking is Edward Frankel of UC Berkeley, and he has an interesting and nuanced view of what such sums mean -- and he gives a shout out to physicists, who don't care what they mean as long as they give the right answers... and they do!.