A012193 sech(arctan(sin(x)))=1-1/2!*x^2+17/4!*x^4-721/6!*x^6+58337/8!*x^8...

1, -1, 17, -721, 58337, -7657441, 1482169457, -396854618161, 140415423261377, -63432792091634881, 35619694647751942097, -24334169873267896659601, 19872330538404158435859617

Offset: 0

Author

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

Keywords

• sign

Programs

Mathematica

With[{nn=30},Take[CoefficientList[Series[Sech[ArcTan[Sin[x]]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* Harvey P. Dale, Jun 06 2018 *)