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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.

A185818 1/5 the number of n X 2 0..4 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.

Table of values

n a(n)
1 1
2 9
3 76
4 656
5 5680
6 49248
7 426928
8 3701360
9 32089696
10 278208816
11 2411993584
12 20911320416
13 181295389360
14 1571781109104
15 13626909445216
16 118141552910384
17 1024254735084784
18 8880006538838880
19 76987211704914352
20 667457928119357552

List of values

[1, 9, 76, 656, 5680, 49248, 426928, 3701360, 32089696, 278208816, 2411993584, 20911320416, 181295389360, 1571781109104, 13626909445216, 118141552910384, 1024254735084784, 8880006538838880, 76987211704914352, 667457928119357552]

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

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