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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.

A254789 The number of unlabeled binary trees that contain n distinct subtrees, where a subtree means take any node and everything below that node.

Table of values

n a(n)
0 1
1 1
2 3
3 15
4 111
5 1119
6 14487
7 230943
8 4395855
9 97608831
10 2482988079
11 71321533887
12 2286179073663
13 80984105660415
14 3144251526824991
15 132867034410319359
16 6073991827274809407
17 298815244349875677183
18 15746949613850439270975
19 885279424331353488224511
20 52902213099156326247243519

List of values

[1, 1, 3, 15, 111, 1119, 14487, 230943, 4395855, 97608831, 2482988079, 71321533887, 2286179073663, 80984105660415, 3144251526824991, 132867034410319359, 6073991827274809407, 298815244349875677183, 15746949613850439270975, 885279424331353488224511, 52902213099156326247243519]

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

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