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A009719 Expansion of tan(tanh(x))/cos(x). 0
1, 3, 17, 371, 11329, 398211, 31717649, 2487281075, 257775723265, 40422383525763, 6249491749613201, 1324448178268807283, 327217658581539104833, 91010297536273890164739, 29953128179590939779490961, 11561544419017955546723388851 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..15.

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Tan[Tanh[x]]/Cos[x], {x, 0, nn}], x]Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Oct 08 2012 *)

CROSSREFS

Sequence in context: A192556 A144033 A098138 * A332758 A023150 A257116

Adjacent sequences:  A009716 A009717 A009718 * A009720 A009721 A009722

KEYWORD

nonn

AUTHOR

R. H. Hardin

EXTENSIONS

Extended and signs tested Mar 15 1997 by Olivier Gérard.

More terms from Harvey P. Dale, Oct 08 2012

STATUS

approved

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Last modified April 15 01:24 EDT 2021. Contains 342974 sequences. (Running on oeis4.)