how can i use Richardson extrapolation procedure (in explicit Euler method)

function suketu

%euler exlicit method

h = 1;

x = 0:h:3;

y1 = [0];

for i = 1:length(x)-1

x(i+1)=x(i)+h;

y1(i+1) =y1(i) + h * f1(x(i), y1(i));

end

function dy = f1(x,y1)

y0 = -1;

dx=0.01;

d = 50;

c1=(y0-(d^2/(d^2+1)));

dy=c1*exp(-dx)+d*(sin(x)/(d^2+1))+d^2*(cos(x)/d^2+1);

end