\[ \begin{flalign} W=\ n\left(n+1\right)\left(n+2\right)\left(n+3\right)+1&& \end{flalign} \] \[ \begin{flalign} \ \ \ =\ n^{4}+6n^{3}+11n^{2}+6n+1&& \end{flalign} \] \[ \begin{flalign} \ \ \ =\ \left(n^{2}+3n+1\right)^{2}&& \end{flalign} \] \[ \begin{flalign} \ \ \ =\ 1+\small\prod_{k=n}^{n+3}k&& \end{flalign} \] \[ \begin{flalign} n\to n+1&& \end{flalign} \] \[ \begin{flalign} n=0　　\color{Blue}←\ 0\le n \le 10　主目盛\ 1&& \end{flalign} \]

\(Desmos\) コピペ用テキストエリア（ Ctrl＋v で貼り付け ）：

W=\ n\left(n+1\right)\left(n+2\right)\left(n+3\right)+1 W=\ n^{4}+6n^{3}+11n^{2}+6n+1 W=\ \left(n^{2}+3n+1\right)^{2} W=\ 1+\prod_{k=n}^{n+3}k n\to n+1 n=0