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A012165 tanh(tan(arcsinh(x)))=x-1/3!*x^3+1/5!*x^5-57/7!*x^7+4513/9!*x^9... 1
1, -1, 1, -57, 4513, -362737, 43685409, -7472568937, 1694762362561, -492370173816033, 178467092014537921, -78960125273223620761, 41880334808869380979041, -26232480244560931030777297 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..200

FORMULA

a(n) ~ (-1)^n * c * (2*n)! / sqrt(n), where c = 0.2423459676113260058762976897... . - Vaclav Kotesovec, Feb 03 2015

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Tanh[Tan[ArcSinh[x]]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Jun 19 2013 *)

CROSSREFS

Sequence in context: A218636 A218240 A281567 * A209512 A132783 A221445

Adjacent sequences:  A012162 A012163 A012164 * A012166 A012167 A012168

KEYWORD

sign

AUTHOR

Patrick Demichel (patrick.demichel(AT)hp.com)

STATUS

approved

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Last modified May 24 18:27 EDT 2022. Contains 354043 sequences. (Running on oeis4.)