

A013136


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


1



2, 16, 544, 40192, 5111296, 994586624, 274584084480, 102058445570048, 49134745327894528, 29743376752794664960, 22111413979264501940224, 19803614205698007369777152, 21031646806008885489451401216
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,1


LINKS



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



KEYWORD

nonn


AUTHOR

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


STATUS

approved



