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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A131892 a(n) is the number of shapes of balanced trees with constant branching factor 6 and n nodes. The node is balanced if the size, measured in nodes, of each pair of its children differ by at most one node.

Table of values

n a(n)
0 1
1 1
2 6
3 15
4 20
5 15
6 6
7 1
8 36
9 540
10 4320
11 19440
12 46656
13 46656
14 699840
15 4374000
16 14580000
17 27337500
18 27337500
19 11390625
20 91125000
21 303750000
22 540000000
23 540000000
24 288000000
25 64000000
26 288000000
27 540000000
28 540000000
29 303750000
30 91125000
31 11390625
32 27337500

List of values

[1, 1, 6, 15, 20, 15, 6, 1, 36, 540, 4320, 19440, 46656, 46656, 699840, 4374000, 14580000, 27337500, 27337500, 11390625, 91125000, 303750000, 540000000, 540000000, 288000000, 64000000, 288000000, 540000000, 540000000, 303750000, 91125000, 11390625, 27337500]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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