This event has been postponed due to coronavirus concerns.
There are lots of places in maths where changing a 2 to a 3 takes a problem from easy or at least understandable to very difficult or even impossible. This talk will explain a few examples of this phenomenon, then speculate wildly about what is going on.
Ben Barber counts the things that don't need to be counted. He likes maths and anything on a stage, preferably at the same time.