The skew_product(w1, w2, A) function computes the noncommutative product  (in this order) in the Ore algebra A.

The skew_power(w, n, A) function computes the nth power of w in the Ore algebra A.

To declare an Ore algebra, use Ore_algebra[skew_algebra], Ore_algebra[shift_algebra], or Ore_algebra[diff_algebra].

These functions are part of the Ore_algebra package, and so can be used in the form skew_product(..) only after performing the command with(Ore_algebra) or with(Ore_algebra,skew_product).  The functions can always be accessed in the long form Ore_algebra[skew_product](..).