%block box product k-th (k=0,1,2,...) power of m-th order u x u x n x ... x n tensor A
%where u must not exceed n
function C=bpowe(A,k)
s=size(A);
if k==0
    C=eyete(s);
elseif k==1
    C=A;
else
    C=bprode(A,A);
    for i=1:k-2
        C=bprode(C,A);
    end
end
