scipy.special
scipy.special.digamma
scipy.special.erf
scipy.special.
poch
Rising factorial (z)_m
The Pochhammer symbol (rising factorial), is defined as:
(z)_m = gamma(z + m) / gamma(z)
For positive integer m it reads:
(z)_m = z * (z + 1) * ... * (z + m - 1)