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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.

A368813 Number of regions in a regular 2n-gon when all vertices are connect by straight lines except for the n lines joining diametrically opposite vertices.

Table of values

n a(n)
1 0
2 1
3 13
4 57
5 171
6 361
7 813
8 1489
9 2215
10 4081
11 6249
12 8329
13 13027
14 17977
15 20221
16 32033
17 41583
18 50545
19 66881
20 83161
21 93871
22 124521
23 150237
24 173233
25 213351
26 251473
27 285445
28 342889
29 397011
30 432121
31 524149
32 598081
33 663103
34 769217
35 867441
36 960121
37 1091723
38 1218889
39 1333489
40 1506321
41 1667799

List of values

[0, 1, 13, 57, 171, 361, 813, 1489, 2215, 4081, 6249, 8329, 13027, 17977, 20221, 32033, 41583, 50545, 66881, 83161, 93871, 124521, 150237, 173233, 213351, 251473, 285445, 342889, 397011, 432121, 524149, 598081, 663103, 769217, 867441, 960121, 1091723, 1218889, 1333489, 1506321, 1667799]

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

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