GammaRegularized[a, z] == (z^a/(E^z Gamma[a])) (1/(z + (1 - a)/ (1 + 1/(z + (2 - a)/(1 + 2/(z + (3 - a)/(1 + 3/(z + \[Ellipsis])))))))) /; !IntervalMemberQ[Interval[{-Infinity, 0}], z]

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2001-10-29