A009751 Expansion of e.g.f. tan(x)*tan(tanh(x)), even powers only.

0, 2, 8, 48, 2176, 72704, 2567168, 320538624, 23648567296, 2869964963840, 550752408829952, 81617924549246976, 20769854695130791936, 5449382125873097867264, 1599364150040158382587904, 573113440182309263706685440, 238664184536900397410937733120

Offset

0,2

Links

G. C. Greubel, Table of n, a(n) for n = 0..240 (terms 0..100 from Vincenzo Librandi)

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Tan[x]*Tan[Tanh[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Feb 07 2014 *)

Prog

(PARI) x='x+O('x^50); v=Vec(serlaplace(tan(x)*tan(tanh(x)))); concat([0], vector(#v\2, n, v[2*n-1])) \\ G. C. Greubel, Feb 12 2018

Crossrefs

Sequence in context: A009741 A322309 A009745 * A356658 A279239 A279109

Adjacent sequences: A009748 A009749 A009750 * A009752 A009753 A009754

Keyword

nonn

Author

R. H. Hardin

Extensions

Extended and signs tested by Olivier Gérard, Mar 15 1997

Prior Mathematica program replaced by and one more term from Harvey P. Dale, Feb 07 2014

Status

approved