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.

A143891 Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric about the diagonal and under 90-degree rotation.

Table of values

n a(n)
0 1
1 2
2 1
3 5
4 2
5 15
6 7
7 68
8 23
9 370
10 104
11 2649
12 571
13 25209
14 4176
15 313503
16 39827
17 5212881
18 500254
19 114569731
20 8348616

List of values

[1, 2, 1, 5, 2, 15, 7, 68, 23, 370, 104, 2649, 571, 25209, 4176, 313503, 39827, 5212881, 500254, 114569731, 8348616]