A009770 Expansion of tanh(log(1+log(1+x))).

0, 1, -2, 5, -11, -16, 656, -9066, 107766, -1222110, 13400544, -137979810, 1199045706, -4684987308, -153270916044, 6326220565560, -169975260810216, 3943603406845656, -83676044951653392, 1624994111075924376

Offset

0,3

Links

Table of n, a(n) for n=0..19.

Formula

a(n) ~ n! * 2 * exp(n) * (-1)^(n+1) * ((sin(n*arctan(sin(1)/(cos(1) - exp(1)))) + exp(1)*sin(1 - n*arctan(sin(1)/(cos(1) - exp(1))))) / (1 + exp(2) - 2*exp(1)*cos(1))^(1 + n/2)). - Vaclav Kotesovec, Jan 24 2015

Mathematica

Tanh[ Log[ 1+Log[ 1+x ] ] ]
CoefficientList[Series[1 - 2/(2 + Log[1 + x]*(2 + Log[1 + x])), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 24 2015 *)

Crossrefs

Sequence in context: A281023 A359399 A118660 * A132121 A070957 A166744

Adjacent sequences: A009767 A009768 A009769 * A009771 A009772 A009773

Keyword

sign,easy

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved