The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A013005 arctanh(arctan(x)+tan(x))=2*x+16/3!*x^3+808/5!*x^5+98432/7!*x^7... 0
 2, 16, 808, 98432, 22498432, 8253398272, 4441967893504, 3295980115392512, 3225082749950656512, 4023514822062532460544, 6233513843421340514123776, 11741363464465799639674126336 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Table of n, a(n) for n=0..11. FORMULA a(n) ~ (2*n)! / r^(2*n+1), where r = 0.4952542103931914966377065988697787139312... is the root of the equation arctan(r)+tan(r) = 1. - Vaclav Kotesovec, Feb 05 2015 MATHEMATICA nn = 20; Table[(CoefficientList[Series[ArcTanh[ArcTan[x] + Tan[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Feb 05 2015 *) CROSSREFS Sequence in context: A013088 A013137 A013990 * A013000 A013178 A306000 Adjacent sequences: A013002 A013003 A013004 * A013006 A013007 A013008 KEYWORD nonn AUTHOR Patrick Demichel (patrick.demichel(AT)hp.com) STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 8 17:47 EDT 2023. Contains 363165 sequences. (Running on oeis4.)