# n-th power of matrices

Is there any way to calculate the n-th power of a (upper unitriangular) matrix in Sage? Here n is an integer variable.

For example, if y=matrix([[1,0,0],[0,1,1],[0,0,1]]), then I want to obtain a formula in n for y^n. In this case this would be y^n=matrix([[1,0,0],[0,1,n],[0,0,1]]).

I tried the following: sage: y=matrix([[1,0,0],[0,1,1],[0,0,1]]); var('n'); sage: y^n

This resulted in the error: "NotImplementedError: non-integral exponents not supported"

Adding sage: assume(n, 'integer') has no effect at all.