Thread: gamma function notation

1. gamma function notation

Hi!
Can someone please give a short explanation for the gamma function notation?
It seems that the big mystery to me is the 't'.

For example, if I wanted to get the gamma of 1.5 them that would be equal to 0.5! and that will be ~ 0.8, but how? As far as I know then that is sqrt(Pi/4), but where does these numbers come from?