Asymptotic Expansions of Exponential Integral function

Question

In NIST equation 8.20.2 what is meant by $(p)_{k}$

$$\mathop{E_{p}}\nolimits\!\left(z\right)\sim\frac{e^{-z}}{z}\sum_{k=0}^{% \infty}(-1)^{k}\frac{\left(p\right)_{k}}{z^{k}},$$

Answer 1

This is the Pochhammer symbol defined in http://dlmf.nist.gov/5.2.iii $$(p)_k = p\cdot(p+1)\cdot(p+1)\dots(p+k-1)=\frac{\Gamma(p+k)}{\Gamma(p)}$$