A009834 Expansion of e.g.f.: tanh(x)*sin(tan(x)) (even part).

0, 2, -4, 38, -3144, -49526, -10349516, -460714706, -91894143376, -6277401116142, -1574511126111380, -81923064774031562, -27289817479229247448, 10031662078758108490394, 3820037980300331336027556, 3713233478960254473261772350, 1785602965553070049822150781152

Offset

0,2

Links

Stefano Spezia, Table of n, a(n) for n = 0..200

Mathematica

nmax=200; expan=Series[Tanh[x]*Sin[Tan[x]]/2, {x, 0, 2*nmax}]; Join[{0}, Table[(2n)! Coefficient[expan, x^(2n)], {n, nmax}]] (* Stefano Spezia, Sep 17 2022 *)

Prog

(PARI) my(x='x+O('x^50), v=Vec(serlaplace(tanh(x)*sin(tan(x))))); concat(0, vector(#v\2, k, v[2*k-1])) \\ Michel Marcus, Sep 17 2022

Crossrefs

Twice A024229.

Sequence in context: A009626 A009835 A362411 * A106127 A018992 A098625

Adjacent sequences: A009831 A009832 A009833 * A009835 A009836 A009837

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved