A013136 tan(tanh(x)+tan(x))=2*x+16/3!*x^3+544/5!*x^5+40192/7!*x^7...

2, 16, 544, 40192, 5111296, 994586624, 274584084480, 102058445570048, 49134745327894528, 29743376752794664960, 22111413979264501940224, 19803614205698007369777152, 21031646806008885489451401216

Offset

0,1

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..200

Vaclav Kotesovec, Graph - abs(e.g.f.) in the complex plane

Formula

a(n) ~ 2 * (2*n+1)! / ((1/(cos(r))^2 + 1/(cosh(r))^2) * r^(2*n+2)), where r = 0.7516422408690037654862466685691510005314750319453074712524... is the root of the equation tanh(r) + tan(r) = Pi/2. - Vaclav Kotesovec, Feb 07 2015

Mathematica

nn = 20; Table[(CoefficientList[Series[Tan[Tan[x] + Tanh[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 07 2015 *)

Crossrefs

Sequence in context: A168404 A013087 A121271 * A013004 A012679 A012726

Adjacent sequences: A013133 A013134 A013135 * A013137 A013138 A013139

Keyword

nonn

Author

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

Status

approved