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.
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
Offset: 0
Links
- Alois P. Heinz, Table of n, a(n) for n = 0..820
Programs
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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);
Comments