ArcTan[z] == z - z^3/(3 + (9 z^2)/(5 + (4 z^2)/(7 + (25 z^2)/ (9 + (16 z^2)/(11 + (49 z^2)/(13 + (36 z^2)/(15 + \[Ellipsis]))))))) /; !IntervalMemberQ[Interval[{-Infinity, -1}], I z] && !IntervalMemberQ[Interval[{1, Infinity}], I z]

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2001-10-29