To be fair, I think i'd probably go completely loopy if I knew that the end of human existence was a mathematical certainty!! I will be very surprised if I am right though coz thinking about it, didn't Hurley go to meet Leonard's friend and find out he had died? I'm sure in that episode it said where Leonard and his friend had heard the numbers - possibly on the radio? - which kinda kills the theory that it was his equation.

Unless it was his equation but he had washed his hands of the whole thing, and then hearing the numbers in that way made him start to go a bit insane?!! (A long shot even for Lost!)