#### Answer

$\frac{4}{3},\frac{8}{5},\frac{16}{9},\frac{32}{17}$

#### Work Step by Step

$a_n = \frac{2^{n+1}}{2^n + 1}$
To find the first four terms, we need to find $a_1, a_2, a_3$, and $a_4$.
$a_1 = \frac{2^{1+1}}{2^1 + 1} = \frac{4}{3}$
$a_2 = \frac{2^{2+1}}{2^2 + 1} = \frac{8}{5}$
$a_3 = \frac{2^{3+1}}{2^3 + 1} = \frac{16}{9}$
$a_4 = \frac{2^{4+1}}{2^4 + 1} = \frac{32}{17}$