A302579 - OEIS

%I #4 Apr 10 2018 14:17:11

%S 1,2,24,632,28784,1991552,193410624,24993180032,4134783110144,

%T 850499728758272,212579274719007744,63381008507902595072,

%U 22200896917210834817024,9019985888570141052280832,4204783981520054371872374784,2228007853953954434037178007552

%N Expansion of e.g.f. exp(cosh(x)/cos(x)-1) (even powers only).

%H N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>

%F a(n) = (2*n)! * [x^(2*n)] exp(cosh(x)/cos(x)-1).

%e exp(cosh(x)/cos(x)-1) = 1 + 2*x^2/2! + 24*x^4/4! + 632*x^6/6! + 28784*x^8/8! + ...

%t nmax = 15; Table[(CoefficientList[Series[Exp[Cosh[x]/Cos[x] - 1], {x, 0, 2 nmax}], x] Range[0, 2 nmax]!)[[n]], {n, 1, 2 nmax + 1, 2}]

%Y Cf. A000795, A005046, A006229, A009234, A009253, A009254, A009274, A012853, A217502.

%K nonn

%O 0,2

%A _Ilya Gutkovskiy_, Apr 10 2018