This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A012237 arctanh(arctan(arctanh(x)))=x+2/3!*x^3+32/5!*x^5+1168/7!*x^7+80768/9!*x^9... 0
 1, 2, 32, 1168, 80768, 8855296, 1420471296, 312821661696, 90619729117184, 33397289918332928, 15260151754256547840, 8466388564521610903552, 5606464118961336397856768, 4368144479139164180218642432 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n) ~ (2*n)! / (tanh(tan(1)))^(2*n+1). - Vaclav Kotesovec, Feb 05 2015 MATHEMATICA nn = 20; Table[(CoefficientList[Series[ArcTanh[ArcTan[ArcTanh[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: A012198 A012114 A055929 * A012093 A012214 A320419 Adjacent sequences:  A012234 A012235 A012236 * A012238 A012239 A012240 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 10 12:25 EST 2019. Contains 329895 sequences. (Running on oeis4.)