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%I #8 Feb 03 2015 15:02:32
%S 1,-1,1,-113,4033,-307297,32041153,-4722808145,919792817281,
%T -229762987386049,71595055755086977,-27226195625057526833,
%U 12411835138553868048961,-6681718218812850626513185
%N arcsinh(sin(sinh(x)))=x-1/3!*x^3+1/5!*x^5-113/7!*x^7+4033/9!*x^9...
%H Vaclav Kotesovec, <a href="/A012031/b012031.txt">Table of n, a(n) for n = 0..226</a>
%F a(n) ~ (2*n)! * (-1)^n * c / (sqrt(n) * (arcsin(log(1+sqrt(2))))^(2*n)), where c = 0.444000919811565867306663265... . - _Vaclav Kotesovec_, Feb 03 2015
%t nn = 20; Table[(CoefficientList[Series[ArcSinh[Sin[Sinh[x]]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* _Vaclav Kotesovec_, Feb 03 2015 *)
%K sign
%O 0,4
%A Patrick Demichel (patrick.demichel(AT)hp.com)
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