Can I find the Fourier series expression from given terms?
For the exponential Fourier series, use the identities:

\$cos(n\omega t)= \dfrac{e^{jn\omega t}+e^{-jn\omega t}}{2}\$

\$sin(n\omega t)= \dfrac{e^{jn\omega t}-e^{-jn\omega t}}{j2}\$

with \$n=1;\:n=3;\:n=11\$, and \$\omega=\frac{4\pi}{3}\$