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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.

A284216 Number of n X 2 0..1 arrays with the number of 1's horizontally or antidiagonally adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero.

Table of values

n a(n)
1 2
2 6
3 19
4 62
5 212
6 751
7 2719
8 10002
9 37258
10 140108
11 530646
12 2021127
13 7733421
14 29702087
15 114438213
16 442099674
17 1711885120
18 6642102554
19 25817134600
20 100506778916
21 391827603432
22 1529486575678
23 5977159139018
24 23382840951503
25 91561688560429
26 358847611430293
27 1407524281467975

List of values

[2, 6, 19, 62, 212, 751, 2719, 10002, 37258, 140108, 530646, 2021127, 7733421, 29702087, 114438213, 442099674, 1711885120, 6642102554, 25817134600, 100506778916, 391827603432, 1529486575678, 5977159139018, 23382840951503, 91561688560429, 358847611430293, 1407524281467975]

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

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