How can I plot the result obtained from Fourier analysis of the figure?

I solved Fourier analysis of a waveform shown in the figure; however, when I try to plot the equation obtained with Fourier analysis I could not see the result as expected. I'm sure that there is no fault in my equation. I think the problem sources from the resolution of the value of "i" in the loop, but I could not figure out the problem exaclty. Could you please correct my codes given below?

Note: The period of the figure is 12pi.

Thanks in advance...

    clear all;close all;clc;
beta = 0:.01:(12*pi);
N=1000;              
y=0;                 
for i=1:1:N                                                   
    y = y+(((1/(6*pi*i))*((-2*cos(12/13*pi*i)+1+2*cos(24/13*pi*i)-cos(36/13*pi*i)+2*cos(4*pi*i)-cos(40/13*pi*i)-2*cos(64/13*pi*i)+2*cos(76/13*pi*i)-2*cos(88/13*pi*i)+2*cos(100/13*pi*i)-2*cos(112/13*pi*i)+cos(124/13*pi*i)+cos(128/13*pi*i)+cos(132/13*pi*i)-cos(140/13*pi*i)-2*cos(144/13*pi*i)+cos(12*pi*i)))*(sin(i*beta))));
end
hold on
y=y+(1/13);
plot(beta,y); grid;