This is a matrix Ei,j where a 1 is placed on every (i,j) cell starting with i=0. Example 0 & 0 & 0& 0& 0& 0& \dots\\ 1 & 0 & 0& 0& 0& 0& \dots\\ 0 & 1 & 0& 0& 0& 0& \dots\\ 0 & 0 & 1& 0& 0& 0& \dots\\ 0 & 0 & 0& 1& 0& 0& \dots\\ \vdots \end{array}\right]$$