The Stirling numbers of the second kind obey the following recursive formula $$\left\{\begin{array}{c}n+1\\r\end{array}\right\}=\left\{\begin{array}{c}n\\r-1\end{array}\right\}+r\cdot \left\{\begin{array}{c}n\\r\end{array}\right\}$$ with the initial conditions $$\begin{align}\left\{\begin{array}{c}n\\n\end{array}\right\}&:=1,\quad n\ge 1\nonumber\\\left\{\begin{array}{c}n\\r\end{array}\right\}&:=0,\quad r=0 < n\text{ or }n < r.\nonumber\end{align}$$
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