OFFSET
0,3
FORMULA
a(n) ~ (-1)^(n+1) * sin(Pi*tanh(1)/2) * tanh(1) * 2^(2*n) * n^(2*n-1) / exp(2*n). - Vaclav Kotesovec, Oct 31 2013
MATHEMATICA
Table[n!*SeriesCoefficient[Cos[ArcSinh[x]*Tan[x]], {x, 0, n}], {n, 0, 40, 2}] (* Vaclav Kotesovec, Oct 31 2013 *)
With[{nn=30}, Take[CoefficientList[Series[Cos[ArcSinh[x]Tan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]]
CROSSREFS
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
EXTENSIONS
More terms from Harvey P. Dale, Dec 16 2017
STATUS
approved