OFFSET
0,2
FORMULA
E.g.f.: exp(2*cos(arccos(1 - 27*x/2)/6) / sqrt(4 - 27*x) - 1).
a(n) ~ 3^(3*n - 1/3) * exp((3/2)^(4/3)*n^(1/3) - n - 5/6) * n^(n - 1/3) / 2^(2*n + 1/6).
MATHEMATICA
CoefficientList[Series[Exp[Sum[Binomial[3*k, k]*x^k, {k, 1, 20}]], {x, 0, 20}], x] * Range[0, 20]!
CoefficientList[Series[Exp[2*Cos[ArcCos[1 - 27*x/2]/6] / Sqrt[4 - 27*x] - 1], {x, 0, 20}], x] * Range[0, 20]!
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Feb 15 2024
STATUS
approved