OFFSET
0,5
EXAMPLE
x + 1/3!*x^3 - 4/4!*x^4 + 33/5!*x^5 - 168/6!*x^6 ...
MATHEMATICA
With[{nn=20}, CoefficientList[Series[Log[Cosh[x]+ArcTanh[x]], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Feb 06 2019 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
a(0)=0 inserted and title improved by Sean A. Irvine, Aug 01 2018
STATUS
approved