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A024297
Expansion of e.g.f. tan(x)*tan(tan(x))/2 (even powers only).
0
0, 1, 12, 344, 18496, 1617152, 209249792, 37538874368, 8908210487296, 2699849585000448, 1017035120794927104, 466006356701359898624, 255181639297776949919744, 164564302025304936925888512
OFFSET
0,3
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
KEYWORD
nonn
AUTHOR
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