login
A012166
arctanh(tan(arcsinh(x))) = x+3/3!*x^3+49/5!*x^5+1915/7!*x^7+143905/9!*x^9...
0
1, 3, 49, 1915, 143905, 17011475, 2994791825, 719040113675, 229441987074625, 92824148885459875, 46824601078366320625, 28633111489683067566875, 20964654070778933185750625, 18047023186844734022903421875
OFFSET
0,2
FORMULA
a(n) ~ (2*n)! * 2^(2*n+1) * exp((2*n+1)*Pi/4) / (exp(Pi/2)-1)^(2*n+1). - Vaclav Kotesovec, Oct 30 2013
MATHEMATICA
Table[n!*SeriesCoefficient[ArcTanh[Tan[ArcSinh[x]]], {x, 0, n}], {n, 1, 40, 2}] (* Vaclav Kotesovec, Oct 30 2013 *)
CROSSREFS
Sequence in context: A012206 A012094 A012059 * A012068 A012126 A203513
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved