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A003228 Endpoints in trees with n nodes.
(Formerly M0351)
5
1, 2, 2, 5, 9, 21, 43, 101, 226, 556, 1333, 3365, 8500, 22007, 57258, 151264, 401761, 1077063, 2902599, 7871250, 21440642, 58672589, 161155637, 444240627, 1228400744, 3406668865, 9472308269, 26402207803, 73755064178 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

R. W. Robinson and A. J. Schwenk, The distribution of trees in a large random tree, Discr. Math., 12 (1975), 359-.

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

LINKS

Table of n, a(n) for n=1..29.

Eric Weisstein's World of Mathematics, Tree Leaf.

Index entries for sequences related to trees

FORMULA

a(n)=sum{k=1 to n} k*c(n, k), where c(n, k) = A055290(n, k) has g.f. (1-x+x*y)*B(x, y)+(1/2)*(B(x^2, y^2)-B(x, y)^2) and B(x, y) is g.f. for A055372.

CROSSREFS

Cf. A000055, A003227, A055290.

Sequence in context: A002990 A060405 A326493 * A184713 A110182 A309867

Adjacent sequences:  A003225 A003226 A003227 * A003229 A003230 A003231

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Corrected and extended with formula by Christian G. Bower, May 25 2000

STATUS

approved

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Last modified November 19 18:39 EST 2019. Contains 329323 sequences. (Running on oeis4.)