how to construct the original signal ?

can you please help me with this ,
with the help of this site i knew how to plot the coeficients of
fourier series expansion of a signal,

now i want to construct the original signal using the coefficients
that were put in a vector called "a"
so i tried this code:

k = -7:8;
a=(1/16)*((sin(5/16*pi.*k))./(sin(pi/16.*k)));
a(k==0) = 5/16;

the above lines shows calulating the coeff in vector "a"

for k=-2:2
for n=-8:7
x=x+a.*exp((j*2*pi.*k.*n)/16);
end
end
stem(x)

the above lines were supposed to sum the coeffs multiplied by
exp((j*2*pi.*k.*n)/16) , where kvaries from -2 to 2 to take only
part of the coeffs to see the effect of increasing the no of coeffs
which will nearly plot the original signal , but unfortunately
nothing happens.

thanks in advance
.