OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..200 (terms 0..50 from Vincenzo Librandi)
FORMULA
a(n) ~ (2*n)! * 4 / (sqrt(4+Pi^2) * (log((Pi+sqrt(4+Pi^2))/2))^(2*n+1)). - Vaclav Kotesovec, Jan 22 2015
MATHEMATICA
f[x_] := Sec@Sinh[x]; Table[Derivative[2*n][f][0], {n, 0, 15}] (* Arkadiusz Wesolowski, Aug 18 2012 *)
With[{nn=30}, Take[CoefficientList[Series[1/Cos[Sinh[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Oct 09 2012 *)
PROG
(PARI) x='x+O('x^50); v=Vec(serlaplace(1/cos(sinh(x)))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 21 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested by Olivier Gérard, Mar 15 1997
a(14), a(15) from Arkadiusz Wesolowski, Aug 18 2012
STATUS
approved