Newton divided rule Method

Given the data x and y, I am require to find the value of y when x is equal to 40. However the code give me the answer is out of range. I would like to know where is the problem thank you.

n = 7;
x = [20,23,34,49,53,58,61];
y = [166,193,212,220,228,241,268];
plot(x,y,'-o')
grid on

x0 = 40;

n = size(x,1);
if n == 1
    n = size(x,2);
end

for i = 1:n
    D(i,1) = y(i);
end

for i = 2:n
    for j = 2:i
        D(i,j)=(D(i,j-1)-D(i-1,j-1))/(x(i)-x(i-j+1));
    end
end

fx0 = D(n,n);
for i = n-1:-1:1
    fx0 = fx0*(x0-x(i)) + D(i,i);
end
fprintf('Newtons iterated value: %11.8f \n', fx0)