A060912 E.g.f.: exp(x*exp(x*exp(x*exp(x*exp(x)))) + 1/2*x^2*exp(x*exp(x*exp(x*exp(x))))^2).

1, 1, 4, 25, 218, 2451, 33112, 516727, 9117180, 179330905, 3890434256, 92271385449, 2374775505016, 65900749176835, 1961009596461840, 62275489622799751, 2101798757669917328, 75111617959762807473

Offset: 0

Author

Vladeta Jovovic, Apr 07 2001

Keywords

• nonn

References

• I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, Wiley, N.Y., 1983.

Crossrefs

Cf. A000949 - A000951, A060905 - A060913.

Formula

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 = 4, m = 2.