A012222 Expansion of e.g.f.: exp(arctan(tanh(x)))=1+x+1/2!*x^2-3/3!*x^3-15/4!*x^4+41/5!*x^5...

1, 1, 1, -3, -15, 41, 561, -1243, -40415, 58001, 4825121, -1956083, -866056815, -740509639, 218527875281, 509169335477, -73838559553215, -295854887910879, 32207514779999041, 189240977761969437

Offset: 0

Author

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

Keywords

• sign

Programs

Mathematica

With[{nn=20},CoefficientList[Series[Exp[ArcTan[Tanh[x]]],{x,0,nn}],x] Range[0,nn]!] (* Harvey P. Dale, Mar 17 2025 *)

Extensions

Definition clarified by Harvey P. Dale, Mar 17 2025