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A012006 -arctanh(log(cos(x))) = 1/2!*x^2+2/4!*x^4+46/6!*x^6+1112/8!*x^8... 0
1, 2, 46, 1112, 63376, 4635872, 523749136, 76049858432, 14634264866176, 3496967323112192, 1032537134569578496, 366067157640456292352, 154146217678162805226496, 75874517780279404503590912 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..13.

MATHEMATICA

Table[n!*SeriesCoefficient[-ArcTanh[Log[Cos[x]]], {x, 0, n}], {n, 2, 40, 2}] (* Vaclav Kotesovec, Oct 25 2013 *)

CROSSREFS

Sequence in context: A066555 A290046 A012001 * A279524 A264500 A173586

Adjacent sequences:  A012003 A012004 A012005 * A012007 A012008 A012009

KEYWORD

nonn

AUTHOR

Patrick Demichel (patrick.demichel(AT)hp.com)

STATUS

approved

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Last modified November 17 00:08 EST 2019. Contains 329209 sequences. (Running on oeis4.)