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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.

A380990 Number of free polyominoes with n cells with at most 4 collinear cell centers on any line in the plane.

Table of values

n a(n)
1 1
2 1
3 2
4 5
5 11
6 31
7 85
8 262
9 764
10 2255
11 6341
12 17221
13 43994
14 106205
15 239367
16 502611
17 977791
18 1771624
19 2989373
20 4687803
21 6819069
22 9234529
23 11622453
24 13527854
25 14571011
26 14643347
27 13747913
28 12041014
29 9905945
30 7763985
31 5805906
32 4139266
33 2858796
34 1971455
35 1368967
36 942226
37 618148
38 368480
39 186275
40 73649
41 20236
42 3476
43 400
44 96
45 27
46 12
47 2
48 1

List of values

[1, 1, 2, 5, 11, 31, 85, 262, 764, 2255, 6341, 17221, 43994, 106205, 239367, 502611, 977791, 1771624, 2989373, 4687803, 6819069, 9234529, 11622453, 13527854, 14571011, 14643347, 13747913, 12041014, 9905945, 7763985, 5805906, 4139266, 2858796, 1971455, 1368967, 942226, 618148, 368480, 186275, 73649, 20236, 3476, 400, 96, 27, 12, 2, 1]

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

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