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A009723
Expansion of tan(tanh(x)/cos(x)).
0
1, 3, 57, 1995, 128881, 12775059, 1796958633, 342118793307, 84276974508769, 26141579246291235, 9956883572644073241, 4570240365824839488747, 2487549038143714062879313, 1584207614996350912703688627
OFFSET
0,2
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, Dec 15 2014 *)
CROSSREFS
Sequence in context: A053774 A254570 A308404 * A069992 A012196 A012090
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested Mar 15 1997 by Olivier Gérard.
Prior Mathematica program replaced by Harvey P. Dale, Dec 15 2014
STATUS
approved