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.

A351615 Number of free polyominoes with n squares, having 180-degree rotational symmetry about the center of a square, and no other symmetry.

Table of values

n a(n)
1 0
2 0
3 0
4 0
5 1
6 0
7 4
8 0
9 19
10 1
11 73
12 4
13 283
14 25
15 1090
16 106
17 4183
18 463
19 16105
20 1892
21 62170
22 7752
23 240907
24 31212
25 936447
26 125609
27 3651618
28 503165
29 14277519
30 2014826
31 55961118
32 8058790
33 219813564
34 32231897
35 865091976
36 128897247
37 3410498446
38 515554767
39 13466262587
40 2062445063
41 53245595410
42 8252868076
43 210800433323

List of values

[0, 0, 0, 0, 1, 0, 4, 0, 19, 1, 73, 4, 283, 25, 1090, 106, 4183, 463, 16105, 1892, 62170, 7752, 240907, 31212, 936447, 125609, 3651618, 503165, 14277519, 2014826, 55961118, 8058790, 219813564, 32231897, 865091976, 128897247, 3410498446, 515554767, 13466262587, 2062445063, 53245595410, 8252868076, 210800433323]

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

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