Hello Penglu,
I'm not sure of what you want to do exactly but you can try this code:
y=0;
for l=1:5
y(l) = y(1)+(4.*l*(1/20).^2.*sin(pi*(1/20))*sin(pi*(1/20)))./(pi^2.*(l.^2-(1/20)^2).*(l.^2-(1/20)^2));
end
disp(y);
More generally use this:
for i = 1:5
y(i)=2*i;
end
