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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.

A056521 Number of primitive (period n) periodic palindromic structures using exactly four different symbols.

Table of values

n a(n)
1 0
2 0
3 0
4 0
5 0
6 1
7 1
8 7
9 10
10 43
11 65
12 219
13 350
14 1058
15 1701
16 4796
17 7770
18 21094
19 34105
20 90205
21 145749
22 379326
23 611501
24 1573205
25 2532530
26 6465123
27 10391735
28 26378849
29 42355950
30 107089814
31 171798901
32 433088656
33 694337225
34 1746623215
35 2798806984
36 7029320466
37 11259666950

List of values

[0, 0, 0, 0, 0, 1, 1, 7, 10, 43, 65, 219, 350, 1058, 1701, 4796, 7770, 21094, 34105, 90205, 145749, 379326, 611501, 1573205, 2532530, 6465123, 10391735, 26378849, 42355950, 107089814, 171798901, 433088656, 694337225, 1746623215, 2798806984, 7029320466, 11259666950]

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

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