I have th following Matlab-Yalmip code:

P=cell(1+m*2,1)
for i=1:m*2+1     
    P{i}=sdpvar(n);                                                                 
end 

phi=cell(1+m*2,1);  
 
for i=1:m*2+1
  phi{i} = A'*P{i}+P{i}*A;
end

for i=1:m*2
  phi{i} = phi{i}+(i)*P{i+1};
end

I Try to construct the following banded Matrix with Matlab:

$ Phi = left(begin{array}{cccccc}
phi_{0} & frac{1}{2}phi_{1} & 0_{n} &  ldots & ldots &0_{n}\
frac{1}{2}phi_{1} & phi_{2} & frac{1}{2}phi_{3} & ddots & &vdots \
0_{n} & frac{1}{2}phi_{3}  & ddots & ddots & ddots&vdots\
vdots& ddots & ddots & ddots & ddots& 0_{n}\
vdots&  & ddots & ddots & phi_{2m-2}  & frac{1}{2}phi_{2m-1}\
0_{n} &  ldots& ldots & 0_{n} &  frac{1}{2}phi_{2m-1}&L_{2m}\
end{array}
right)_{(m+1)ntimes(m+1)n}$

Please, Can you help me hwo efficently construct $Phi$