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A009708 Expansion of tan(tan(x)/cos(x)). 0
1, 7, 177, 10519, 1108833, 180134183, 41643888145, 12982974409271, 5247381641852609, 2667871676330509895, 1666128949779524612977, 1253728661849677130856279, 1118729647152655182634160673 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..12.

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Tan[Tan[x]/Cos[x]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Oct 13 2014 *)

CROSSREFS

Sequence in context: A152930 A027489 A098433 * A231490 A231489 A221110

Adjacent sequences: A009705 A009706 A009707 * A009709 A009710 A009711

KEYWORD

nonn

AUTHOR

R. H. Hardin

EXTENSIONS

Extended and signs tested by Olivier Gérard, Mar 15 1997

Prior Mathematica program replaced by Harvey P. Dale, Oct 13 2014

STATUS

approved

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Last modified January 27 21:49 EST 2023. Contains 359849 sequences. (Running on oeis4.)