${\rm E}_n$ function for non-integer $n$

Question

The ${\rm E}_n$ function implementation in scipy is valid only for positive integer values of $n$, but I have an expression with real $n$ to evaluate. Is there an expression for ${\rm E}_n$ in terms of other special functions (preferably implemented in scipy, but I can do my own homework on that front)?

Answer 1

It can be stated in terms of the upper incomplete Gamma function: $$E_\alpha(x)=x^{\alpha-1}\Gamma(1-\alpha,x)$$ Or you can look on stack overflow!