x = 2:0.2:4;
v = vander(x);
u = v(:,11-5:11);
y = sum(u');
a = (u'*u)\(u'*y')

a =

   1.00000017837590
   0.99999731404223
   1.00001595230769
   0.99995331974803
   1.00006726440287
   0.99996183281005

u = v(:,11-6:11);
y = sum(u');
a = (u'*u)\(u'*y')
Warning: Matrix is close to singular or badly scaled.
         Results may be inaccurate. RCOND = 2.337960e-17.

a =

   0.99997464146416
   1.00045741872700
   0.99660034498889
   1.01332056418028
   0.97099001879468
   1.03328584898733
   0.98428343198428

u = v(:,11-8:11);
y = sum(u');
a = (u'*u)\(u'*y')
Warning: Matrix is close to singular or badly scaled.
         Results may be inaccurate. RCOND = 5.266425e-25.

a =

   1.0e+03 *

   0.00135381489493
  -0.00749502319083
   0.08956078130055
  -0.52249685205043
   1.91979951101377
  -4.46402450290450
   6.44181355670735
  -5.26420274975354
   1.86835087719298

diary off