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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.

A230648 Number of nX4 0..2 white square subarrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value 2-x(i,j).

Table of values

n a(n)
1 0
2 9
3 21
4 123
5 531
6 2547
7 11745
8 54957
9 255753
10 1192623
11 5557191
12 25901847
13 120714693
14 562609041
15 2622085629
16 12220512675
17 56954899323
18 265444104699
19 1237128910377
20 5765764156725
21 26871924749169
22 125239314486231

List of values

[0, 9, 21, 123, 531, 2547, 11745, 54957, 255753, 1192623, 5557191, 25901847, 120714693, 562609041, 2622085629, 12220512675, 56954899323, 265444104699, 1237128910377, 5765764156725, 26871924749169, 125239314486231]

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

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