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 A009691 Expansion of tan(tan(sinh(x))) (odd powers only). 0
 1, 5, 113, 5781, 520001, 72300997, 14337027825, 3838128112661, 1332896717838849, 582503435362842629, 312774761747765633777, 202388665054249928155157, 155314408487077603685528641 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Table of n, a(n) for n=1..13. FORMULA a(n) ~ (2*n-1)! * 8 / ((4+Pi^2) * sqrt(1+arctan(Pi/2)^2) * arcsinh(arctan(Pi/2))^(2*n)). - Vaclav Kotesovec, Jan 23 2015 MATHEMATICA Tan[ Tan[ Sinh[ x ] ] ] (* Odd Part *) nn = 20; Table[(CoefficientList[Series[Tan[Tan[Sinh[x]]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Jan 23 2015 *) CROSSREFS Sequence in context: A279838 A009603 A009678 * A194570 A210908 A355074 Adjacent sequences: A009688 A009689 A009690 * A009692 A009693 A009694 KEYWORD nonn AUTHOR R. H. Hardin EXTENSIONS Extended and signs tested Mar 15 1997 by Olivier Gérard. Offset changed to 1 by Vaclav Kotesovec, Jan 23 2015 STATUS approved

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Last modified December 5 00:23 EST 2023. Contains 367565 sequences. (Running on oeis4.)