

A009796


Expansion of tanh(sin(x))*tan(x).


1



0, 2, 4, 198, 4488, 365834, 26333836, 3548101326, 521011775760, 109600356362258, 26637313430995732, 8227982193974569686, 2954555247298219357848, 1270556471466981784144154
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OFFSET

0,2


LINKS

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


FORMULA

a(n) ~ (2*n)! * (1)^(n+1) * 4 * Pi / ((4 + Pi^2) * (log((Pi + sqrt(4 + Pi^2))/2))^(2*n+1)).  Vaclav Kotesovec, Jan 24 2015


MATHEMATICA

Tanh[ Sin[ x ] ]*Tan[ x ] (* Even Part *)
nn = 20; Table[(CoefficientList[Series[Tan[x]*Tanh[Sin[x]], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Jan 24 2015 *)


CROSSREFS

Sequence in context: A018637 A018647 A009743 * A018651 A068479 A116010
Adjacent sequences: A009793 A009794 A009795 * A009797 A009798 A009799


KEYWORD

sign


AUTHOR

R. H. Hardin


EXTENSIONS

Extended with signs by Olivier Gérard, Mar 15 1997


STATUS

approved



