A009016 Expansion of E.g.f.: cos(cosh(x)*x) (even powers only).

1, -1, -11, -61, 1737, 88679, 2086525, -45950997, -9763133167, -705668046769, -17356978593659, 3823112141007763, 788728947108214489, 82036502117747569079, 1412038521698998808077

Offset: 0

Author

R. H. Hardin

Keywords

• sign

Links

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

Programs

Mathematica

With[{nmax = 60}, CoefficientList[Series[Cos[x*Cosh[x]], {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* G. C. Greubel, Jul 21 2018 *)

PARI

x='x+O('x^60); v=Vec(serlaplace(cos(x*cosh(x)))); vector(#v\2,n,v[2*n-1]) \\ G. C. Greubel, Jul 21 2018

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997