$\"\"$

The series is $\"\"$ .

Rewrite the series as $\"\"$ .

The maclaurin series of $\"\"$ is $\"\"$ , $\"\"$ .

$\"\"$ .

Compare the series with exponential series.

The series is in the form of exponential series.

Here $\"\"$ .

$\"\"$ .

$\"\"$

The sum of series $\"\"$ .