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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.

A134018 Let P(A) be the power set of an n-element set A. Then a(n) = the number of pairs of elements {x,y} of P(A) for which either 0) x and y are disjoint and for which either x is a subset of y or y is a subset of x, or 1) x and y are intersecting but for which x is not a subset of y and y is not a subset of x.

Table of values

n a(n)
0 0
1 1
2 3
3 10
4 45
5 226
6 1113
7 5230
8 23565
9 102826
10 438273
11 1836550
12 7601685
13 31183426
14 127084233
15 515429470
16 2083077405
17 8396552026
18 33779262993
19 135696871990
20 544528258725
21 2183337968626
22 8749031918553
23 35043178292110
24 140313885993645
25 561679104393226

List of values

[0, 1, 3, 10, 45, 226, 1113, 5230, 23565, 102826, 438273, 1836550, 7601685, 31183426, 127084233, 515429470, 2083077405, 8396552026, 33779262993, 135696871990, 544528258725, 2183337968626, 8749031918553, 35043178292110, 140313885993645, 561679104393226]

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

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