A060911 E.g.f.: exp(x*exp(x*exp(x*exp(x))) + 1/2*x^2*exp(x*exp(x*exp(x)))^2).

1, 1, 4, 25, 218, 2331, 29152, 417607, 6746700, 121312441, 2401341056, 51857779689, 1212621122176, 30509979042115, 821524617293304, 23563369209520711, 717014609781379568, 23064363484845390513

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 = 3, m = 2.