A012177 tan(tan(arctanh(x)))=x+6/3!*x^3+176/5!*x^5+11792/7!*x^7...

1, 6, 176, 11792, 1399808, 258010112, 68048472064, 24288413734912, 11265869660880896, 6584336654436794368, 4732528038730841194496, 4101916559962554300891136, 4218542156655644369974460416

Offset

0,2

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..195

Formula

a(n) = 8*(2*n+1)! / ((4+Pi^2) * cosh(arctan(Pi/2))^2 * tanh(arctan(Pi/2))^(2*n+2)). - Vaclav Kotesovec, Feb 06 2015

Mathematica

nn = 20; Table[(CoefficientList[Series[Tan[Tan[ArcTanh[x]]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 06 2015 *)

Crossrefs

Sequence in context: A071095 A134632 A024277 * A012227 A012152 A165928

Adjacent sequences: A012174 A012175 A012176 * A012178 A012179 A012180

Keyword

nonn

Author

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

Status

approved