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 A012152 arctanh(tan(tan(x)))=x+6/3!*x^3+176/5!*x^5+12240/7!*x^7... 0
 1, 6, 176, 12240, 1561088, 318007808, 94807748608, 38942692972544, 21088169713729536, 14558790290337431552, 12481351528273319821312, 13009249833253480856289280, 16200881782506627598590672896 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n) ~ (2*n)! / (arctan(Pi/4))^(2*n+1). - Vaclav Kotesovec, Feb 05 2015 MATHEMATICA nn = 20; Table[(CoefficientList[Series[ArcTanh[Tan[Tan[x]]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 05 2015 *) CROSSREFS Sequence in context: A024277 A012177 A012227 * A165928 A024278 A062240 Adjacent sequences:  A012149 A012150 A012151 * A012153 A012154 A012155 KEYWORD nonn AUTHOR Patrick Demichel (patrick.demichel(AT)hp.com) STATUS approved

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Last modified January 27 11:59 EST 2021. Contains 340465 sequences. (Running on oeis4.)