A024297 Expansion of e.g.f. tan(x)*tan(tan(x))/2 (even powers only).

0, 1, 12, 344, 18496, 1617152, 209249792, 37538874368, 8908210487296, 2699849585000448, 1017035120794927104, 466006356701359898624, 255181639297776949919744, 164564302025304936925888512

Offset

0,3

Links

Table of n, a(n) for n=0..13.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Tan[x]Tan[Tan[x]]/2, {x, 0, nn}], x] Range[ 0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Mar 18 2023 *)

Prog

(PARI) x='x+O('x^40); v=Vec(serlaplace(tan(x)*tan(tan(x))/2)); concat([0], vector(#v\2, n, v[2*n-1])) \\ Michel Marcus, Mar 13 2019

Crossrefs

Cf. A009750.

Sequence in context: A231520 A305108 A027015 * A077296 A080481 A209425

Adjacent sequences: A024294 A024295 A024296 * A024298 A024299 A024300

Keyword

nonn

Author

R. H. Hardin

Extensions

Extended and signs tested March 1997.

Name edited by Michel Marcus, Mar 13 2019

Prior Mathematica program replaced by Harvey P. Dale, Mar 18 2023

Status

approved