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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.

A289269 Number of polygonal tiles with n sides with two exits per side and n edges connecting pairs of exits, with no edges between exits on the same side and non-isomorphic under rotational and reflectional, i.e. dihedral, symmetry.

Table of values

n a(n)
1 0
2 2
3 4
4 19
5 80
6 638
7 6054
8 76692
9 1137284
10 19405244
11 370597430
12 7825459362
13 180862277352
14 4540781512946
15 123053646087312
16 3580073396748560
17 111297799861936256
18 3682093529146577694
19 129163727524848878358
20 4788738149626920381804
21 187102616692953377567060

List of values

[0, 2, 4, 19, 80, 638, 6054, 76692, 1137284, 19405244, 370597430, 7825459362, 180862277352, 4540781512946, 123053646087312, 3580073396748560, 111297799861936256, 3682093529146577694, 129163727524848878358, 4788738149626920381804, 187102616692953377567060]

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

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