A009090 Expansion of e.g.f. cos(tanh(x))/exp(x).

1, -1, 0, 2, 4, -36, -56, 944, 1744, -41104, -86208, 2650592, 6199744, -237023424, -608357504, 28021573376, 77889982720, -4225816615168, -12588540708864, 790713657219584, 2503565961032704, -179579770991391744

Offset: 0

Author

R. H. Hardin

Keywords

• sign
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 0..250

Programs

Magma

m:=30; R:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(Cos(Tanh(x))/Exp(x))); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Jul 25 2018

Mathematica

With[{nmax = 30}, CoefficientList[Series[Cos[Tanh[x]]/Exp[x], {x, 0, nmax}], x]*Range[0, nmax]!] (* G. C. Greubel, Jul 25 2018 *)

PARI

x='x+O('x^30); Vec(serlaplace(cos(tanh(x))/exp(x))) \\ G. C. Greubel, Jul 25 2018

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997