ArcTan[z] == z/(1 + z^2 - (2 z^2)/(3 - (2 z^2)/(5 (1 + z^2) - (12 z^2)/(7 - (12 z^2)/(9 (1 + z^2) - (30 z^2)/ (11 - (30 z^2)/(13 (1 + z^2) - \[Ellipsis]))))))) /; !IntervalMemberQ[Interval[{-Infinity, -1}], I z] && !IntervalMemberQ[Interval[{1, Infinity}], I z]

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2001-10-29