x(n) is a vector function where n is all the intergers from -infinity to +infinity. nv(n-1) is n*v(n-1) which is the multiplication of two vectors. Again n is all integers from -infinity to +infinity and v(n-1) is the vector function v(n) after all the elements have been shifted over one position to the right.
At least that's what it looks like form my position.