% 
% Written by:
% -- 
% John L. Weatherwax                2007-07-01
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

clc; 

M = [ 
     0 1 1 1 0 ; 
     0 0 1 0 1 ; 
     0 0 0 1 1 ; 
     0 1 0 0 0 ; 
     1 0 0 1 0 ; 
    ]; 

M^2
Pm = M + M^2 

sum( Pm, 2 )