\"\"

\

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 \"\".