>>>The guy has to be insane.
>>
>>Not necessarily :).
>>
>>As soon as people think you are, the things look more complicated than they really are. Squaring a 5-digit number like he did is really reduced into a binomial squared (i.e. 57000**2+2*57000*683+683**2) so it becomes one 2-digit squaring, one 3-digit squaring, one 2x3 digit multiplication and then adding it all up. I never really practiced stuff like that, but just doing a lot of that on a calculator makes you lazy with your fingers, so sick of typing it you start doing it in your mind. My problem would rather be that of stack, i.e. memorizing the intermediate results, but that's a skill which can be acquired.
>
>I know how he does it x^2 + 2(x*y) + y^2 but that is still a whole heck of a lot of mental gymnastics. Not only does he have to do the math in his head, he as to remember the numbers that each of the other operations resulted in. He has a very strange mind.

#define strange :)

Yep, memorizing the intermediate results is the hard part. Which is why I can't do it :).