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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.

A368598 Number of non-isomorphic n-element sets of singletons or pairs of elements of {1..n}, or unlabeled loop-graphs with n edges and up to n vertices.

Table of values

n a(n)
0 1
1 1
2 2
3 6
4 17
5 52
6 173
7 585
8 2064
9 7520
10 28265
11 109501
12 437394
13 1799843
14 7629463
15 33302834
16 149633151
17 691702799
18 3287804961
19 16058229900
20 80533510224
21 414384339438
22 2185878202630
23 11811050484851
24 65318772618624
25 369428031895444
26 2135166786135671
27 12601624505404858

List of values

[1, 1, 2, 6, 17, 52, 173, 585, 2064, 7520, 28265, 109501, 437394, 1799843, 7629463, 33302834, 149633151, 691702799, 3287804961, 16058229900, 80533510224, 414384339438, 2185878202630, 11811050484851, 65318772618624, 369428031895444, 2135166786135671, 12601624505404858]

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

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