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A009723
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Expansion of tan(tanh(x)/cos(x)).
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0
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1, 3, 57, 1995, 128881, 12775059, 1796958633, 342118793307, 84276974508769, 26141579246291235, 9956883572644073241, 4570240365824839488747, 2487549038143714062879313, 1584207614996350912703688627
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OFFSET
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0,2
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LINKS
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Table of n, a(n) for n=0..13.
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MATHEMATICA
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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 *)
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CROSSREFS
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Sequence in context: A053774 A254570 A308404 * A069992 A012196 A012090
Adjacent sequences: A009720 A009721 A009722 * A009724 A009725 A009726
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin
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EXTENSIONS
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Extended and signs tested Mar 15 1997 by Olivier Gérard.
Prior Mathematica program replaced by Harvey P. Dale, Dec 15 2014
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STATUS
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approved
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