Polygamma $\psi ^{(n)}(x)$

Returns the polygamma function of the first argument $x$, with the order $n$ being given by the floor of the second argument.

$$\psi^{(n)}(x)=\frac{d^{n+1}}{dx^{n+1}}\ln\Gamma(x)$$

It relationship to the derivative of the Gamma function (and factorials) is why Minsky provides this function.