INPUT:
 1/4  3/4  3/4  1/4
a_(-1) a_0  a_1  a_2

n = 2

G_n*x = 1*x =>  (G-I)*x = 0

sum_j x_j = 1

eig(G)

OUTPUT:

x = [0 1/8 1/2 3/4 1/2 1/8 0]

(n=1
0 1/2 1/2 0)

INPUT:

1/8 1/2 3/4 1/2 1/8
%(downsampling by 2)
1/8  3/4  1/8

% center in the index 0
L = toeplitz(3/4 1/8 0 0 ... 0 1/8)