A012391 arcsinh(tan(x)*tan(x))=2/2!*x^2+16/4!*x^4+152/6!*x^6-5504/8!*x^8...

0, 2, 16, 152, -5504, -865888, -49313024, 10192998272, 4634262163456, 729893872005632, -280859292338008064, -286057930617679095808, -94104910901654903619584, 51677977224364973979901952

Offset: 0

Author

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

Keywords

• sign

Links

• Vaclav Kotesovec, Table of n, a(n) for n = 0..220

Programs

Mathematica

With[{nn=30},Take[CoefficientList[Series[ArcSinh[Tan[x]^2],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* Harvey P. Dale, Dec 14 2014 *)

Extensions

Prepended a(0)=0 by Vaclav Kotesovec, Nov 28 2015