$\"\"$

\

The series is $\"\"$ .

\

If $\"\"$ convergence, then $\"\"$ .

\

Find $\"\"$ .

\

$\"\"$

\

$\"\"$

\

If $\"\"$ then $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$ .

\

Therefore, the sequence is divergent.

\

$\"\"$

\

$\"\"$ is divergent.