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A012174 Expansion of e.g.f.: exp(tan(arctanh(x)))=1+x+1/2!*x^2+5/3!*x^3+17/4!*x^4+121/5!*x^5... 0
1, 1, 1, 5, 17, 121, 721, 6621, 56545, 636337, 7062241, 94260341, 1283497841, 19853570985, 319471153457, 5628171840461, 104260273696961, 2063430523313761, 43168502192389825, 949149114720943077 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..19.

MATHEMATICA

With[{nn=20}, CoefficientList[Series[Exp[Tan[ArcTanh[x]]], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Dec 27 2016 *)

CROSSREFS

Sequence in context: A009240 A180387 A324411 * A202038 A012259 A256459

Adjacent sequences:  A012171 A012172 A012173 * A012175 A012176 A012177

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

Definition clarified by Harvey P. Dale, Dec 27 2016

STATUS

approved

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Last modified September 20 01:58 EDT 2019. Contains 327207 sequences. (Running on oeis4.)