A012203 E.g.f.: exp(arctan(arctan(x))) = 1+x+1/2!*x^2-3/3!*x^3-15/4!*x^4+49/5!*x^5...

1, 1, 1, -3, -15, 49, 609, -1859, -48031, 119617, 6247681, -10283171, -1214813487, 678311217, 330587407201, 246695568861, -120086685689663, -270153706006015, 56186566871496961, 221300400903581245

Offset

0,4

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Mathematica

With[{nn=20}, CoefficientList[Series[Exp[ArcTan[ArcTan[x]]], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Aug 14 2014 *)

Crossrefs

Sequence in context: A124161 A089580 A034564 * A112586 A043005 A165746

Adjacent sequences: A012200 A012201 A012202 * A012204 A012205 A012206

Keyword

sign

Author

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

Extensions

Definition edited and clarified by Harvey P. Dale, Aug 14 2014

Status

approved