j=sqrt(-1); 
  f=1; 
  for k=1:2:20 
     c(k)=(-2*j)/k*pi 
  end 
  for k=2:2:20 
      c(k)=0 
  end 
  disp(c(k)); 
  t=1; 
  x(1)=c(k)*exp(j*2*pi*k*t*1) 
  for t=1:20 
     for k=1:2:20; 
         k=1; 
  x(t)=c(k)*exp(j*2*pi*k*f*t);  
  k=k+2; 
     end 
  end 
  disp(x(t))