OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..232
FORMULA
a(n) ~ (2*n-1)! * 4 * tan(arcsinh(Pi/2)) / (sqrt(4+Pi^2) * arcsinh(Pi/2)^(2*n)). - Vaclav Kotesovec, Jan 24 2015
MATHEMATICA
nn = 20; Table[(CoefficientList[Series[Sec[Sinh[x]]*Tan[x], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Jan 24 2015 *)
PROG
(PARI) x='x+O('x^50); v=Vec(serlaplace(tan(x)/cos(sinh(x)))); vector((#v-1)\2 , n, v[2*n-1]) \\ G. C. Greubel, Feb 12 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested by Olivier Gérard, Mar 15 1997
Changed offset to 1 by Vaclav Kotesovec, Jan 24 2015
STATUS
approved