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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.

A202069 Number of arrays of n+2 integers in -1..1 with sum zero and the sum of every adjacent pair being odd.

Table of values

n a(n)
1 2
2 4
3 2
4 0
5 6
6 12
7 6
8 0
9 20
10 40
11 20
12 0
13 70
14 140
15 70
16 0
17 252
18 504
19 252
20 0
21 924
22 1848
23 924
24 0
25 3432
26 6864
27 3432
28 0
29 12870
30 25740
31 12870
32 0
33 48620
34 97240
35 48620
36 0
37 184756
38 369512
39 184756
40 0
41 705432
42 1410864
43 705432
44 0
45 2704156
46 5408312
47 2704156
48 0
49 10400600

List of values

[2, 4, 2, 0, 6, 12, 6, 0, 20, 40, 20, 0, 70, 140, 70, 0, 252, 504, 252, 0, 924, 1848, 924, 0, 3432, 6864, 3432, 0, 12870, 25740, 12870, 0, 48620, 97240, 48620, 0, 184756, 369512, 184756, 0, 705432, 1410864, 705432, 0, 2704156, 5408312, 2704156, 0, 10400600]

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

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