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A012251 exp(arcsinh(arctan(x)))=1+x+1/2!*x^2-2/3!*x^3-11/4!*x^4+24/5!*x^5... 2
1, 1, 1, -2, -11, 24, 349, -720, -22455, 40320, 2465241, -3628800, -416217603, 479001600, 100729124469, -87178291200, -33198564667887, 20922789888000, 14328891118054449, -6402373705728000, -7852649782447649403 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..20.

FORMULA

E.g.f.: Q(0)-1, where Q(k) =  2 + arctan(x)/(1 - arctan(x)/Q(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Dec 19 2013

MATHEMATICA

With[{nn=30}, CoefficientList[Series[Exp[ArcSinh[ArcTan[x]]], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Oct 26 2011 *)

CROSSREFS

Bisections are (-1)^n*A010050 and (-1)^n*A012138.

Sequence in context: A220281 A009189 A012213 * A241238 A077482 A141428

Adjacent sequences:  A012248 A012249 A012250 * A012252 A012253 A012254

KEYWORD

sign

AUTHOR

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

STATUS

approved

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Last modified December 19 10:16 EST 2014. Contains 252186 sequences.