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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.

A186161 1/4 the number of n X 2 0..3 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 7
3 48
4 321
5 2175
6 14748
7 99933
8 677283
9 4590168
10 31108893
11 210834267
12 1428886932
13 9683993481
14 65631317487
15 444803049600
16 3014563174089
17 20430595384935
18 138464249604684
19 938413592805957
20 6359909317239723

List of values

[1, 7, 48, 321, 2175, 14748, 99933, 677283, 4590168, 31108893, 210834267, 1428886932, 9683993481, 65631317487, 444803049600, 3014563174089, 20430595384935, 138464249604684, 938413592805957, 6359909317239723]

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

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