login
A013318
arctanh(exp(x)-cos(x))=x+2/2!*x^2+3/3!*x^3+24/4!*x^4+165/5!*x^5...
0
0, 1, 2, 3, 24, 165, 1202, 12663, 149744, 1945065, 29307362, 489387723, 8915702664, 178036818765, 3852374482322, 89628609049983, 2235770536642784, 59498096957789265, 1681835781220294082
OFFSET
0,3
FORMULA
a(n) ~ (n-1)! / (2 * r^n), where r = 0.60134676772581981740108057557172913327... is the root of the equation exp(r)-cos(r) = 1. - Vaclav Kotesovec, Feb 05 2015
MATHEMATICA
CoefficientList[Series[ArcTanh[E^x - Cos[x]], {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Feb 05 2015 *)
CROSSREFS
Sequence in context: A003221 A359951 A013312 * A374858 A372737 A193338
KEYWORD
nonn
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
Offset changed to 0 and added a(0)=0 by Vaclav Kotesovec, Feb 05 2015
STATUS
approved