\[x_{n} = \frac{2n - 1}{3}\]
\[x_{2} = (2 \cdot 2 - 1)\ :3 = 3\ :3 = 1;\]
\[x_{5} = (2 \cdot 5 - 1)\ :3 = 9\ :3 = 3;\]
\[x_{10} = (2 \cdot 10 - 1)\ :3 = 19\ :3 =\]
\[= 6\frac{1}{3}.\]