\geq 0,\ i=5,6$$
%
% $\pmatrix{x_1& x_2& 0&0\cr x_2&x_4&x_2+x_3& 0\cr 0&x_2+x_3& x_4&x_3\cr
% 0&0&x_3&x_1}\succeq 0$
%
% To define this example, we can again use Matlab's anonymous functions:

function [penm] = bex3()
  B = sparse(4,4);
  A{1} = sparse([1 0 0 0; 0 0 0 0; 0 0 0 0; 0 0 0 1]);
  A{2} = sparse([0 1 0 0; 1 0 1 0; 0 1 0 0; 0 0 0 0]);
  A{3} = sparse([0 0 0 0; 0 0 1 0; 0 1 0 1; 0 0 1 0]);
  A{4} = sparse([0 0 0 0; 0 1 0 0; 0 0 1 0; 0 0 0 0]);
  A{5} = sparse(4,4);
  A{6} = sparse(4,4