階乗冪(上昇階乗・下降階乗)の１項間漸化式
(1)
\[ P(x+1,y)=\frac{x+1}{x-y+1}P(x,y) \](2)
\[ P(x-1,y)=\frac{x-y}{x}P(x,y) \](3)
\[ P(x,y+1)=(x-y)P(x,y) \](4)
\[ P(x,y-1)=\frac{1}{x-y+1}P(x,y) \](5)
\[ Q(x+1,y)=\frac{x+y}{x}Q(x,y) \](6)
\[ Q(x-1,y)=\frac{x-1}{x+y-1}Q(x,y) \](7)
\[ Q(x,y+1)=(x+y)Q(x,y) \](8)
\[ Q(x,y-1)=\frac{1}{x+y-1}Q(x,y) \](1)
\begin{align*} P(x+1,y) & =\frac{(x+1)!}{(x+1-y)!}\\ & =\frac{x+1}{x+1-y}\frac{x!}{(x-y)!}\\ & =\frac{x+1}{x-y+1}P(x,y) \end{align*}(2)
\begin{align*} P(x-1,y) & =\frac{(x-1)!}{(x-1-y)!}\\ & =\frac{x-y}{x}\frac{x!}{(x-y)!}\\ & =\frac{x-y}{x}P(x,y) \end{align*}(3)
\begin{align*} P(x,y+1) & =\frac{x!}{(x-y-1)!}\\ & =(x-y)\frac{x!}{(x-y)!}\\ & =(x-y)P(x,y) \end{align*}(4)
\begin{align*} P(x,y-1) & =\frac{x!}{(x-y+1)!}\\ & =\frac{1}{x-y+1}\frac{x!}{(x-y)!}\\ & =\frac{1}{x-y+1}P(x,y) \end{align*}(5)
\begin{align*} Q(x+1,y) & =\frac{(x+1+y-1)!}{(x+1-1)!}\\ & =\frac{x+y}{x}\frac{(x+y-1)!}{(x-1)!}\\ & =\frac{x+y}{x}Q(x,y) \end{align*}(6)
\begin{align*} Q(x-1,y) & =\frac{(x-1+y-1)!}{(x-1-1)!}\\ & =\frac{x-1}{x+y-1}\frac{(x+y-1)!}{(x-1)!}\\ & =\frac{x-1}{x+y-1}Q(x,y) \end{align*}(7)
\begin{align*} Q(x,y+1) & =\frac{(x+y+1-1)!}{(x-1)!}\\ & =(x+y)\frac{(x+y-1)!}{(x-1)!}\\ & =(x+y)Q(x,y) \end{align*}(8)
\begin{align*} Q(x,y-1) & =\frac{(x+y-1-1)!}{(x-1)!}\\ & =\frac{1}{x+y-1}\frac{(x+y-1)!}{(x-1)!}\\ & =\frac{1}{x+y-1}Q(x,y) \end{align*}ページ情報
| タイトル | 階乗冪(上昇階乗・下降階乗)の１項間漸化式 |
| URL | https://www.nomuramath.com/n0lg5oq0/ |
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階乗冪(下降階乗・上昇階乗)の差分
\[
P(x,y)=\frac{1}{y+1}\left(P(x+1,y+1)-P(x,y+1)\right)
\]
階乗冪(上昇階乗・下降階乗)同士の関係
\[
P(x,y)=P^{-1}(x-y,-y)
\]
階乗冪(下降階乗・上昇階乗)の指数法則
\[
P(x,y+z)=P(x,y)P(x-y,z)
\]
階乗冪(下降階乗・上昇階乗)の1/2値
\[
P\left(-\frac{1}{2},n\right)=\frac{(-1)^{n}(2n-1)!}{2^{2n-1}(n-1)!}
\]