function Aeq = is_stat_sym(n)
Aeq = zeros(0,2^n);
rind = 0;
for i=1:n
  for s=[-1,+1]
    rind = rind + 1;
    for xi = 1:2^n
      x = i2c(xi,n);
      x = x*s;
      Aeq(rind,xi) = x(i);
    end
  end
end
return



function c=i2c(i,n)
dims = repmat(2,[1 n]);
c = ind2coord(i,dims);
c = c-1;
c = 2*c-1;
return