1,2

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

Zvonkine, D., Counting ramified coverings and intersection theory on Hurwitz spaces II (local structure of Hurwitz spaces and combinatorial results). Moscow Mathematical Journal, vol. 7 (2007), no. 1, 135-162.

Zvonkine, D., Enumeration of ramified coverings of the sphere and 2-dimensional gravity, Prepint 2004.

Zvonkine, D., An algebra of power series arising in the intersection theory of moduli spaces of curves and in the enumeration of ramified coverings of the sphere. Preprint 2004.

T. D. Noe, Table of n, a(n) for n=1..100

J. Riordan and N. J. A. Sloane, Enumeration of rooted trees by total height, J. Austral. Math. Soc., vol. 10 pp. 278-282, 1969.

D. Zvonkine, Home Page

Index entries for sequences related to rooted trees

Index entries for sequences related to trees

E.g.f: (LambertW(-x)/(1+LambertW(-x)))^2 - Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 10 2001

a(n)=sum(k=1, n-1, binomial(n, k)*(n-k)^(n-k)*k^k) - Benoit Cloitre (benoit7848c(AT)orange.fr), Mar 22 2003

A001864 := proc(n) local k; add(n!*n^k/k!, k=0..n-2); end;

(PARI) a(n)=sum(k=1, n-1, binomial(n, k)*(n-k)^(n-k)*k^k)

Cf. A000435, A001863.

Sequence in context: A135389 A065513 A119491 this_sequence A099045 A013523 A081065

Adjacent sequences: A001861 A001862 A001863 this_sequence A001865 A001866 A001867

nonn,easy,nice

N. J. A. Sloane (njas(AT)research.att.com).