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Con $\ds{0 < a < 1}$:
\begin{align}
&\color{#66f}{\large\sum_{k_{1}=1}^{10}\ldots\sum_{k_{100}=1}^{10}
\delta_{k_{1}\ +\ \cdots\ +\ x_{100},700}}
=\sum_{k_{1}=1}^{10}\ldots\sum_{k_{100}=1}^{10}\oint_{\verts{z}\ =\ a}
{1 \over z^{-k_{1}\ -\ \cdots\ -\ k_{100}\ +\ 701}}\,{\dd z \más de 2\pi\ic}
\\[3 mm]&=\oint_{\verts{z}\ =\ a}
{1 \over z^{701}}\,\pars{\sum_{k =1}^{10}z^{k}}^{100}\,{\dd z \más de 2\pi\ic}
=\oint_{\verts{z}\ =\ a}{1 \over z^{701}}\,\pars{z\,{z^{10} - 1 \sobre z - 1}}^{100}
\,\,{\dd z \más de 2\pi\ic}
\\[3 mm]&=\oint_{\verts{z}\ =\ a}{1 \over z^{601}}\,
{\pars{1 - z^{10}}^{100} \ \pars{1 - z}^{100}}\,\,{\dd z \más de 2\pi\ic}
\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\pars{1}
\\[3 mm]&=\sum_{n = 0}^{100}\sum_{k = 0}^{\infty}\pars{-1}^{n + k}{100 \elegir n}
{-100 \elegir k}\oint_{\verts{z}\ =\ a}{1 \over z^{601 - 10n - k}}
\,{\dd z \más de 2\pi\ic}
\\[3 mm]&=\sum_{n = 0}^{100}\sum_{k = 0}^{\infty}\pars{-1}^{n + k}{100 \elegir n}
\pars{-1}^{k}{k + 99 \elegir 99}\delta_{10n + k,600}
=\sum_{n = 0}^{100}\pars{-1}^{n}{100 \elegir n}{699 - 10n \elegir 99}
\end{align}
Contribuciones a la suma están limitados por $\quad\ds{0 \leq n \leq 100}\quad$
y $\quad\ds{99 \leq 699 - 10n}\quad$ que producen $\quad\ds{0 \leq n \leq 60}$:
$$
\color{#66f}{\large\sum_{k_{1}=1}^{10}\ldots\sum_{k_{100}=1}^{10}
\delta_{k_{1}\ +\ \cdots\ +\ x_{100},700}
=\sum_{n = 0}^{60}\pars{-1}^{n}{100 \elegir n}{699 - 10n \elegir 99}}
$$
que es de $\ds{\pars{~\mbox{ver la expresión}\ \pars{1}~}}$, equivalente a $\ds{\bracks{z^{600}}\pars{1 - z^{10} \over 1 - z}^{100}}$.
Esto lleva a que el valor
\begin{align}&
{\tt 1.211306391075837746814517416259229640857139892912601984348493171327624}
\\
&{\tt 03014516376282321342995 \times 10^{92}}
\end{align}
Se encuentra con W & Una.