Coding for summation of Fourier transform

clc
clear all
close all
L = 1;
n = [-4:4];
syms x
rectn = rectangularPulse(-1,1,x);
F_rectn = fourier(rectn);
rp1 = real(F_rectn)*cos(2*pi*n*x/L);
F_0 = F_rectn(x==0);
y1 = zeros(1, numel(n));
for i = numel(n);
    y1 = y1 + real(F_rectn).*cos(2*pi*n(i)*x/L);
end
y1 = y1 + F_0;
fplot(y1)

Hi all, I checked my code many times, but it returns the error of summation. Can anyone help me fix the code like the formula in the picture but eliminate the imaginary part?