A012530 arctanh(sinh(x)*sin(x)) = 2/2!*x^2+232/6!*x^6+685472/10!*x^10...

2, 232, 685472, 11496925312, 641870470410752, 90115671250751137792, 26741121618547455928082432, 14898765702188922919730883100672, 14301272675149517137926114108443328512, 22156614594176569412220482693952524899581952

Offset: 0

Author

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

Keywords

• nonn

Crossrefs

Bisection of A009359. - Olivier Gérard, Jun 04 2012

Programs

Mathematica

Table[n!*SeriesCoefficient[ArcTanh[Sinh[x]*Sin[x]],{x,0,n}],{n,2,40,4}] (* Vaclav Kotesovec, Nov 02 2013 *)

Formula

a(n) ~ 2*(4*n+1)! / r^(4*n+2), where r = 1.00572817652562... is the root of the equation sinh(r)*sin(r) = 1. - Vaclav Kotesovec, Oct 24 2013