SymPy Gamma

SymPy:

product (i,(i,1,k),(k,1,n))

$\prod_{\substack{1 \leq i \leq k\\1 \leq k \leq n}} i$

Result:

(Product(factorial(k), (k, 1, n))).doit()

See what Wolfram|Alpha has to say.

Experiment with SymPy at SymPy Live.