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 A009691 Expansion of tan(tan(sinh(x))) (odd powers only). 0

%I #13 Jan 23 2015 16:55:11

%S 1,5,113,5781,520001,72300997,14337027825,3838128112661,

%T 1332896717838849,582503435362842629,312774761747765633777,

%U 202388665054249928155157,155314408487077603685528641

%N Expansion of tan(tan(sinh(x))) (odd powers only).

%F 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

%t Tan[ Tan[ Sinh[ x ] ] ] (* Odd Part *)

%t 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 *)

%K nonn

%O 1,2

%A _R. H. Hardin_

%E Extended and signs tested Mar 15 1997 by _Olivier GĂ©rard_.

%E Offset changed to 1 by _Vaclav Kotesovec_, Jan 23 2015

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Last modified March 3 00:46 EST 2024. Contains 370499 sequences. (Running on oeis4.)