Casio fx 991ms Factorial I apologize if this is the wrong forum for this, but I can't find the answer through google.
I'm wondering how to find factorials on my casio f-991MS calculator. Any help is much appreciated. 

I have a Casio fx-991D.  Like many calculators, it has an ${}_nP_r$ key, in this case at the SHIFT of the multiplication button. One can calculate $n!$ by using ${}_nP_n$. So $n$ gets entered twice, which is not much of a nuisance. 
