And a good book to work your way though is the following:

http://www.amazon.com/Programming-Mathematica-Introduction-Paul-Wellin/dp/1107009464/

I think that Szabolcs would agree with me that the next important step for you would be to spend time learning (by working through a course like this book or the on-line course that he pointed you to) how to program in Mathematica--and essential to this is to work many examples. Good luck!

Hi Alice,

Daniel is of course correct, and perhaps has better sense than I do in that he gave you a direct answer to your question. But I would also like to point out that Mathematica offers a significantly different paradigm in programming compared to mainly procedural languages like C. It does of course have Do, For, and While -- and these are still useful in some calculations, especially where results are built up in an iteration, like you are doing calculating N factorial.

But I usually call Mathematica a 10th generation language. (I started calling it that somewhere around V4, so maybe I should increment that!) As an example, below are a few more ways to calculate N Factorial.

Kind regards and enjoy Mathematica,

David

In[1]:= (* by recursion *)
fact1[1] = 1;

In[2]:= fact1[n_] := n fact1[n - 1];

In[3]:= fact1[3]

Out[3]= 6

In[4]:= (* by Apply *)
fact2[n_] := Times @@ Range[1, n]

In[5]:= fact2[3]

Out[5]= 6

In[6]:= (* and of course by built in *)
Factorial[3]

Out[6]= 6

In[7]:= (* or *)
3!

Out[7]= 6