\[{{}_{p}H_{q}}\left({a_{1},\dots,a_{p}\atop b_{1},\dots,b_{q}};z\right)=\sum_{k%
=-\infty}^{\infty}\frac{{\left(a_{1}\right)_{k}}\dots{\left(a_{p}\right)_{k}}}%
{{\left(b_{1}\right)_{k}}\dots{\left(b_{q}\right)_{k}}}z^{k}.\]