cp's OEIS Frontend

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.

A239820 Number of 2Xn 0..3 arrays with no element equal to zero plus the sum of elements to its left or one plus the sum of the elements above it, modulo 4.

Table of values

n a(n)
1 5
2 23
3 132
4 729
5 3951
6 21602
7 118253
8 646306
9 3532732
10 19315270
11 105601487
12 577330665
13 3156353205
14 17256335056
15 94343160597
16 515789128277
17 2819903064231
18 15416868881838
19 84286524854294
20 460808121256380
21 2519312876415017

List of values

[5, 23, 132, 729, 3951, 21602, 118253, 646306, 3532732, 19315270, 105601487, 577330665, 3156353205, 17256335056, 94343160597, 515789128277, 2819903064231, 15416868881838, 84286524854294, 460808121256380, 2519312876415017]

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

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