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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.

A056519 Number of primitive (period n) periodic palindromic structures using exactly three different symbols.

Table of values

n a(n)
1 0
2 0
3 0
4 1
5 1
6 5
7 6
8 18
9 25
10 63
11 90
12 202
13 301
14 650
15 965
16 2016
17 3025
18 6220
19 9330
20 18970
21 28495
22 57650
23 86526
24 174210
25 261624
26 525693
27 788945
28 1582462
29 2375101
30 4759482
31 7141686
32 14300976
33 21457735
34 42951825
35 64439003
36 128946888
37 193448101
38 387037370
39 580606145
40 1161485370

List of values

[0, 0, 0, 1, 1, 5, 6, 18, 25, 63, 90, 202, 301, 650, 965, 2016, 3025, 6220, 9330, 18970, 28495, 57650, 86526, 174210, 261624, 525693, 788945, 1582462, 2375101, 4759482, 7141686, 14300976, 21457735, 42951825, 64439003, 128946888, 193448101, 387037370, 580606145, 1161485370]

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

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