SciPy

scipy.special.gammaincc

scipy.special.gammaincc(a, x) = <ufunc 'gammaincc'>

Complemented incomplete gamma integral

Defined as:

1 / gamma(a) * integral(exp(-t) * t**(a-1), t=x..inf) = 1 - gammainc(a,x)

a must be positive and x must be >= 0.