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A229394 Number of shapes of balanced 9-ary trees with n nodes, where a tree is balanced if the total number of nodes in subtrees corresponding to the branches of any node differ by at most one. 2
1, 1, 9, 36, 84, 126, 126, 84, 36, 9, 1, 81, 2916, 61236, 826686, 7440174, 44641044, 172186884, 387420489, 387420489, 13947137604, 223154201664, 2082772548864, 12496635293184, 49986541172736, 133297443127296, 228509902503936, 228509902503936, 101559956668416 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n) = 1 for n in { A002452 }.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..820

MAPLE

a:= proc(n) option remember; local m, r; if n<2 then 1 else

      r:= iquo(n-1, 9, 'm'); binomial(9, m) *a(r+1)^m *a(r)^(9-m) fi

    end:

seq(a(n), n=0..91);

CROSSREFS

Column k=9 of A221857.

Cf. A175673.

Sequence in context: A175673 A285198 A230212 * A173682 A009522 A045851

Adjacent sequences:  A229391 A229392 A229393 * A229395 A229396 A229397

KEYWORD

nonn,look

AUTHOR

Alois P. Heinz, Sep 21 2013

STATUS

approved

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Last modified May 10 04:45 EDT 2021. Contains 343748 sequences. (Running on oeis4.)