Usage:
<nbyn_commuting n j A B
Create a ring with a generic pair of n by n commuting matrices, A, B.
Parameters:
n = size of the matrices
Output values:
A, B = two n by n matrices with indeterminate entries.
j = ideal in a new ring containing the entries of the matrix AB-BA.
The new ring has variables a[i,j] and b[i,j].