x(n)=x(x+1)(x+2)⋯(x+n−1)=∏k=0n−1(x+k)superscript𝑥𝑛𝑥𝑥1𝑥2⋯𝑥𝑛1superscriptsubscriptproduct𝑘0𝑛1𝑥𝑘x^{(n)}=x(x+1)(x+2)\cdots(x+n-1)=\prod_{k=0}^{n-1}(x+k)