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A012107
arctanh(arcsin(sinh(x)))=x+4/3!*x^3+84/5!*x^5+4432/7!*x^7+432144/9!*x^9...
0
1, 4, 84, 4432, 432144, 67336512, 15330202432, 4799825862912, 1978228668612864, 1038257514383795200, 676117122084133770240, 534973800492211106598912, 505535479689176978173726720
OFFSET
0,2
FORMULA
a(n) ~ (2*n)! / (arcsinh(sin(1)))^(2*n+1). - Vaclav Kotesovec, Feb 05 2015
MATHEMATICA
nn = 20; Table[(CoefficientList[Series[ArcTanh[ArcSin[Sinh[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: A012139 A012037 A012025 * A012189 A012076 A173211
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved