Function pochhammer 

pub fn pochhammer<P, E, V>(z: V, m: V) -> V
where
    E: FloatElement,
    V: FloatVector<Element = E> + SpecializedTranscendentalMath<E> + SpecializedRealSpecialMath<E>,
    P: Policy,

$(z)_m = \Gamma(z+m)/\Gamma(z)$, the Pochhammer symbol, for real z and real m.