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 A134306 Shapes of height-balanced AVL trees of height at most 6 with n nodes. 3
 0, 1, 1, 2, 1, 4, 6, 4, 17, 32, 44, 60, 70, 184, 476, 872, 1553, 2720, 4288, 6312, 9004, 16088, 36900, 82984, 174374, 346048, 653096, 1199384, 2160732, 3812464, 6617304, 11307920, 18978577, 31327104, 50882720, 80963520, 125489856, 188637520, 273984664 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 REFERENCES F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Camb. 1998, p. 239, Eq 79, A_5. R. C. Richards, Shape distribution of height-balanced trees, Info. Proc. Lett., 17 (1983), 17-20. LINKS Alois P. Heinz, Table of n, a(n) for n = 0..64 Wikipedia, AVL tree FORMULA a(n) = Sum_{h=0..6} A143897(h,n). MAPLE a:= proc(n) local B, z; B:= proc (x, y, d) if d>=1 then x+B(x^2+2*x*y, x, d-1) else x fi end; coeff(B(z, 0, 6), z, n) end: seq (a(n), n=0..64); CROSSREFS Cf. A006265, A036662. Sequence in context: A217299 A217300 A036662 * A006265 A131452 A111104 Adjacent sequences:  A134303 A134304 A134305 * A134307 A134308 A134309 KEYWORD nonn,fini,full AUTHOR Alois P. Heinz, Aug 27 2008 STATUS approved

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