ArcCoth[z] == 1/ (z (1 - 1/(z^2 (3 - 4/(z^2 (5 - 9/(z^2 (7 - 16/(z^2 (9 - 25/(z^2 (11 - 36/(z^2 (13 - \[Ellipsis])))))))))))))) /; !IntervalMemberQ[Interval[{-1, 1}], z]

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2001-10-29