It is known that
\sum\limits_{k = 0}^\infty {\frac{{N^k }}{{k!}}} = e^N
I am looking for any asymptotic approximation which gives
\sum\limits_{k = 0}^M {\frac{{N^k }}{{k!}}} = ?
where M\leq N an integer.
This is not an homework
It is known that
\[\sum\limits_{k = 0}^\infty {\frac{{N^k }}
{{k!}}} = e^N
\]
My question is
\[\sum\limits_{k = 0}^M {\frac{{N^k }}
{{k!}}} = ?
\]
where $M\leq N$ an integer.
This is not an homework