A013172 exp(arctanh(x)+tan(x))=1+2*x+4/2!*x^2+12/3!*x^3+48/4!*x^4+232/5!*x^5...

1, 2, 4, 12, 48, 232, 1344, 8960, 68096, 580480, 5489024, 57192960, 649853952, 8028368896, 106867367936, 1530617461760, 23404867387392, 381866595811328, 6602987646386176, 120993556601405440

Offset

0,2

Links

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

Formula

a(n) ~ 2*exp(tan(1)) * n^n / exp(n). - Vaclav Kotesovec, Oct 24 2013

Mathematica

CoefficientList[Series[Exp[ArcTanh[x]+Tan[x]], {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Oct 24 2013 *)

Crossrefs

Sequence in context: A172452 A004527 A002871 * A321009 A052849 A098558

Adjacent sequences: A013169 A013170 A013171 * A013173 A013174 A013175

Keyword

nonn

Author

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

Status

approved