$2+4+8+16+...+$ till $\frac{n}{2}$ terms=?

Question

$2+4+8+16+...+$ till $\frac{n}{2}$ terms=?

Accepted Answer

$2^{\frac{n+2}{2}}-2$

Answer

$2^{n}$

Answer

$2^{\frac{n}{2}}+2$

Answer

None of these