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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 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS R. W. Robinson and A. J. Schwenk, The distribution of trees in a large random tree, Discr. Math., 12 (1975), 359-372. Eric Weisstein's World of Mathematics, Tree Leaf. FORMULA a(n) = Sum_{k=1..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, A055372. Sequence in context: A002990 A060405 A326493 * A184713 A110182 A309867 Adjacent sequences:  A003225 A003226 A003227 * A003229 A003230 A003231 KEYWORD nonn AUTHOR EXTENSIONS Corrected and extended with formula by Christian G. Bower, May 25 2000 STATUS approved

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Last modified September 24 19:51 EDT 2020. Contains 337321 sequences. (Running on oeis4.)