\[\boxed{\mathbf{820}.}\]
\[e \approx 2 + \frac{1}{2} + \frac{1}{2 \bullet 3} + \frac{1}{2 \bullet 3 \bullet 4} +\]
\[+ \ldots + \frac{1}{2 \bullet 3 \bullet 4 \bullet \ldots \bullet n}\]
\[1)\ \ n = 7:\]
\[e \approx 2 + \frac{1}{2} + \frac{1}{6} + \frac{1}{24} + \frac{1}{120} +\]
\[+ \frac{1}{720} + \frac{1}{5040} \approx 2,7182539\]
\[2)\ \ n = 8:\]
\[e \approx 2 + \frac{1}{2} + \frac{1}{6} + \frac{1}{24} + \frac{1}{120} +\]
\[+ \frac{1}{720} + \frac{1}{5040} +\]
\[+ \frac{1}{40\ 320} \approx 2,7182788\]
\[3)\ Если\ n = 9,\ тогда:\]
\[e \approx 2 + \frac{1}{2} + \frac{1}{6} + \frac{1}{24} + \frac{1}{120} +\]
\[+ \frac{1}{720} + \frac{1}{5040} + \frac{1}{40\ 320} +\]
\[+ \frac{1}{362\ 880} \approx 2,7182815\]
\[4)\ n = 10:\]
\[e \approx 2 + \frac{1}{2} + \frac{1}{6} + \frac{1}{24} + \frac{1}{120} +\]
\[+ \frac{1}{720} + \ldots + \frac{1}{362\ 880} +\]
\[+ \frac{1}{3\ 628\ 800} \approx 2,7182819\]