clear all;
nnn=1024;
a=0.01;
for i=1:nnn
II(i)=i;
X(i)=1.0;
end;
Y(1)=0.0;
Z(i)=0.0;
for i=2:nnn
Y(i)=Y(i-1)+(X(i)-Y(i-1)-Z(i-1))*a*4;
Z(i)=Z(i-1)+Y(i)*a;
figure(1);
plot(II,Y,'r',II,Z,'b');
grid on;