OFFSET
0,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..120
FORMULA
a(n) = 2 * A009837(n).
MATHEMATICA
With[{nn=40}, Take[CoefficientList[Series[Tanh[x]Tan[x], {x, 0, nn}], x] Range[0, nn-2]!, {3, -1, 4}]] (* Harvey P. Dale, May 02 2012 *)
PROG
(Magma)
m:=50; R<x>:=PowerSeriesRing(Rationals(), m);
b:= Coefficients(R!(Laplace( Tan(x)*Tanh(x) )));
[b[4*n-3]: n in [1..Floor((m-2)/4)]]; // G. C. Greubel, Jan 31 2022
(Sage) [factorial(4*n+2)*( tanh(x)*tan(x) ).series(x, 4*n+3).list()[4*n+2] for n in (0..20)] # G. C. Greubel, Jan 31 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested by Olivier Gérard, Mar 15 1997
More terms from Harvey P. Dale, May 02 2012
STATUS
approved