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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.

A209409 Number of subsets of {1,...,n} containing {a,a+2,a+4} for some a.

Table of values

n a(n)
0 0
1 0
2 0
3 0
4 0
5 4
6 15
7 37
8 87
9 200
10 448
11 992
12 2160
13 4628
14 9823
15 20699
16 43335
17 90246
18 187068
19 386192
20 794560
21 1629944
22 3334975
23 6808073
24 13870191
25 28207552
26 57274368
27 116129280
28 235165632
29 475678200
30 961190943
31 1940470231
32 3914210127
33 7889613022
34 15891777084

List of values

[0, 0, 0, 0, 0, 4, 15, 37, 87, 200, 448, 992, 2160, 4628, 9823, 20699, 43335, 90246, 187068, 386192, 794560, 1629944, 3334975, 6808073, 13870191, 28207552, 57274368, 116129280, 235165632, 475678200, 961190943, 1940470231, 3914210127, 7889613022, 15891777084]

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

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