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.

A233020 Number of n X 2 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally, vertically, diagonally or antidiagonally, and top left element zero.

Table of values

n a(n)
1 3
2 15
3 81
4 435
5 2337
6 12555
7 67449
8 362355
9 1946673
10 10458075
11 56183721
12 301834755
13 1621541217
14 8711375595
15 46799960409
16 251422553235
17 1350712686993
18 7256408541435
19 38983468081161
20 209430157488675
21 1125117723605697

List of values

[3, 15, 81, 435, 2337, 12555, 67449, 362355, 1946673, 10458075, 56183721, 301834755, 1621541217, 8711375595, 46799960409, 251422553235, 1350712686993, 7256408541435, 38983468081161, 209430157488675, 1125117723605697]

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

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