A012147 arctanh(tan(sin(x)))=x+3/3!*x^3+41/5!*x^5+1467/7!*x^7+100625/9!*x^9...

1, 3, 41, 1467, 100625, 11103155, 1795927225, 400540116971, 117802787966241, 44174901566136419, 20571101104110689353, 11646565567973048707867, 7878351005250269762378801, 6275481526065593121954975251

Offset

0,2

Links

Table of n, a(n) for n=0..13.

Formula

a(n) ~ (2*n)! / (arcsin(Pi/4))^(2*n+1). - Vaclav Kotesovec, Feb 05 2015

Mathematica

nn = 20; Table[(CoefficientList[Series[ArcTanh[Tan[Sin[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: A207993 A187540 A012104 * A012011 A277453 A147797

Adjacent sequences: A012144 A012145 A012146 * A012148 A012149 A012150

Keyword

nonn

Author

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

Status

approved