A009396 Expansion of log(1+tanh(x)*sin(x)).

0, 2, -24, 742, -46424, 4924442, -795624324, 182148217942, -56122289514224, 22395847873848242, -11236967462922272124, 6923916000862956967342, -5139905036702596261514024, 4524378924970721231979687242

Offset

0,2

Links

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

Formula

a(n) ~ (2*n)! * (-1)^(n+1) / (n * r^(2*n)), where r = 0.82560766907116185156994603327818731... is the root of the equation cos(r) = tanh(r). - Vaclav Kotesovec, Jan 23 2015

Mathematica

Log[ 1+Tanh[ x ]*Sin[ x ] ] (* Even Part *)
nn = 20; Table[(CoefficientList[Series[Log[1 + Sin[x]*Tanh[x]], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Jan 23 2015 *)

Crossrefs

Sequence in context: A012161 A009724 A177771 * A338188 A274634 A292694

Adjacent sequences: A009393 A009394 A009395 * A009397 A009398 A009399

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved