I guess this particular definition of A is just an example, right? If it's really about these specific values, the final result will just be
F=(1:8)'+5;
If you cannot take this shortcut, you'll either need to store all A matrices (right now you overwrite them in each iteration) or you save the respective value in each iteration.
Option 1:
A=zeros(3,3,8);
for m=1:8
a=5+m; b=3*m;
A(:,:,m)=[a, b a*b; b, a+b, a-b; 2-a, 3+b a];
end
F=squeeze(A(1,1,:));
Option 2:
F=zeros(8,1);
for m=1:8
a=5+m; b=3*m;
A=[a, b a*b; b, a+b, a-b; 2-a, 3+b a];
F(m)=A(1);
end
