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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.

A047163 Number of nonempty subsets of {1,2,...,n} in which exactly 1/4 of the elements are <= n/2.

Table of values

n a(n)
1 0
2 0
3 0
4 0
5 2
6 3
7 12
8 16
9 40
10 50
11 110
12 135
13 315
14 392
15 980
16 1232
17 3080
18 3864
19 9480
20 11850
21 29040
22 36300
23 89870
24 112519
25 280423
26 351351
27 876603
28 1098188
29 2741102
30 3433703
31 8586788
32 10758608
33 26965808
34 33794504
35 84844280
36 106344792
37 267298650
38 335061789
39 843098172
40 1056924666

List of values

[0, 0, 0, 0, 2, 3, 12, 16, 40, 50, 110, 135, 315, 392, 980, 1232, 3080, 3864, 9480, 11850, 29040, 36300, 89870, 112519, 280423, 351351, 876603, 1098188, 2741102, 3433703, 8586788, 10758608, 26965808, 33794504, 84844280, 106344792, 267298650, 335061789, 843098172, 1056924666]

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

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