OFFSET
0,4
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..250
FORMULA
a(n) = Sum_{k=0..n/2} binomial(n,2*k)*(2*k)^(n-2*k)*(-1)^k, n>0, a(0)=1. - Vladimir Kruchinin, Jun 29 2011
MATHEMATICA
With[{nmax = 50}, CoefficientList[Series[Cos[x*Exp[x]], {x, 0, nmax}], x]*Range[0, nmax]!] (* G. C. Greubel, Jul 21 2018 *)
PROG
(Maxima)
a(n):=if n=0 then 1 else sum(binomial(n, 2*k)*(2*k)^(n-2*k)*(-1)^k, k, 0, n/2); /* Vladimir Kruchinin, Jun 29 2011 */
(PARI) x='x+O('x^30); Vec(serlaplace(cos(x*exp(x)))) \\ G. C. Greubel, Jul 21 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(Cos(x*Exp(x)))); [Factorial(n-1)*b[n]: n in [1..m]]; // G. C. Greubel, Jul 21 2018
CROSSREFS
KEYWORD
sign,easy
AUTHOR
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
STATUS
approved