cp's OEIS Frontend

A060908 E.g.f.: exp(x*exp(x*exp(x)) + 1/2*x^2*exp(x*exp(x))^2).

%I A060908 #12 May 10 2013 12:44:44
%S A060908 1,1,4,25,194,1791,19312,237637,3280524,50136049,839267936,
%T A060908 15255154179,298936866736,6277386102703,140540145723720,
%U A060908 3339966073612921,83936496568012208,2223184658988286113,61877234830148427808
%N A060908 E.g.f.: exp(x*exp(x*exp(x)) + 1/2*x^2*exp(x*exp(x))^2).
%C A060908 a(n) = the number of functions f:{1,2,...,n} -> {1,2,...,n} such that the functional digraphs have cycle lengths at most 2 and no element is at a distance of more than 2 form a cycle. - _Geoffrey Critzer_, Sep 23 2012
%D A060908 I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, Wiley, N.Y., 1983.
%F A060908 E.g.f.: exp(Sum_{d|m} T_k^d/d), where T_k = x*exp(T_(k - 1)), k >= 1, T_0 = x; k = 2, m = 2.
%t A060908 nn=20; a=x Exp[x]; b=x Exp[a]; t=Sum[n^(n-1)x^n/n! ,{n, 1, nn}]; Range[0,nn]! CoefficientList[Series[Exp[b+b^2/2], {x, 0, nn}], x]  (* _Geoffrey Critzer_, Sep 23 2012 *)
%Y A060908 Cf. A000949-A000951, A060905-A060913.
%K A060908 nonn
%O A060908 0,3
%A A060908 _Vladeta Jovovic_, Apr 07 2001