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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.

A221864 Number of forests (sets) of rooted labeled trees on {1,2,...,n} such that the node with label 1 is in the same rooted tree as the node with label 2.

Table of values

n a(n)
0 0
1 0
2 2
3 11
4 88
5 930
6 12254
7 193736
8 3576564
9 75552560
10 1797906490
11 47601571968
12 1388102588048
13 44210926113536
14 1527152437488150
15 56867807937459200
16 2271048787266451756
17 96826981390532388864
18 4389830567318703987314
19 210886652765343862784000

List of values

[0, 0, 2, 11, 88, 930, 12254, 193736, 3576564, 75552560, 1797906490, 47601571968, 1388102588048, 44210926113536, 1527152437488150, 56867807937459200, 2271048787266451756, 96826981390532388864, 4389830567318703987314, 210886652765343862784000]

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

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