Product[expr, {iiminimax}]
evaluates the discrete product of expr with i ranging from imin to imax.
Product[expr, {iimax}]
same as Product[expr, {i, 1, imax}].
Product[expr, {iiminimaxdi}]
i ranges from imin to imax in steps of di.
Product[expr, {iiminimax}, {jjminjmax}, ...]
evaluates expr as a multiple product, with {i, ...}, {j, ...}, ... being in outermost-to-innermost order.

Symbolic products involving the factorial are evaluated:

Evaluate the nth primorial: