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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.

A199127 Number of n X 2 0..2 arrays with values 0..2 introduced in row major order, the number of instances of each value within one of each other, and no element equal to any horizontal or vertical neighbor.

Table of values

n a(n)
1 1
2 2
3 2
4 12
5 30
6 30
7 210
8 560
9 560
10 4200
11 11550
12 11550
13 90090
14 252252
15 252252
16 2018016
17 5717712
18 5717712
19 46558512
20 133024320
21 133024320
22 1097450640
23 3155170590
24 3155170590
25 26293088250
26 75957810500
27 75957810500
28 638045608200

List of values

[1, 2, 2, 12, 30, 30, 210, 560, 560, 4200, 11550, 11550, 90090, 252252, 252252, 2018016, 5717712, 5717712, 46558512, 133024320, 133024320, 1097450640, 3155170590, 3155170590, 26293088250, 75957810500, 75957810500, 638045608200]

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

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