A012391 - OEIS

A012391

arcsinh(tan(x)*tan(x))=2/2!*x^2+16/4!*x^4+152/6!*x^6-5504/8!*x^8...

0, 2, 16, 152, -5504, -865888, -49313024, 10192998272, 4634262163456, 729893872005632, -280859292338008064, -286057930617679095808, -94104910901654903619584, 51677977224364973979901952

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OFFSET

0,2

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..220

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[ArcSinh[Tan[x]^2], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Dec 14 2014 *)

CROSSREFS

Sequence in context: A209021 A209056 A209213 * A012387 A009518 A052674

Adjacent sequences: A012388 A012389 A012390 * A012392 A012393 A012394

KEYWORD

sign

AUTHOR

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

EXTENSIONS

Prepended a(0)=0 by Vaclav Kotesovec, Nov 28 2015

STATUS

approved