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A000060 Number of signed trees with n nodes.
(Formerly M0904 N0340)
5
1, 2, 3, 10, 27, 98, 350, 1402, 5743, 24742, 108968, 492638, 2266502, 10600510, 50235931, 240882152, 1166732814, 5702046382, 28088787314, 139355139206, 695808554300, 3494391117164, 17641695461662, 89495028762682, 456009893224285, 2332997356507678, 11980753878699716, 61739654456234062, 319188605907760846 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

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

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

LINKS

T. D. Noe, Table of n, a(n) for n=1..500

F. Harary and G. Prins, The number of homeomorphically irreducible trees and other species, Acta Math., 101 (1959), 141-162.

P. Leroux and B. Miloudi, Generalisations de la formule d'Otter, Ann. Sci. Math. Qu├ębec, Vol. 16, No. 1, pp. 53-80, 1992.

Index entries for sequences related to trees

FORMULA

G.f.: S(x)+S(x^2)-S(x)^2, where S(x) is the generating function for A000151. - Pab Ter (pabrlos2(AT)yahoo.com), Oct 12 2005

MAPLE

unassign('x'): with(combstruct): norootree:=[S, {B = Set(S), S = Prod(Z, B, B)}, unlabeled]: S:=x->add(count(norootree, size=i)*x^i, i=1..30): seq(coeff(S(x)+S(x^2)-S(x)^2, x, i), i=1..29); # with Algolib (Pab Ter)

CROSSREFS

Sequence in context: A052929 A151415 A134588 * A089752 A264759 A171190

Adjacent sequences:  A000057 A000058 A000059 * A000061 A000062 A000063

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Pab Ter (pabrlos2(AT)yahoo.com), Oct 12 2005

STATUS

approved

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Last modified August 21 00:36 EDT 2017. Contains 290855 sequences.