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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.

A110105 a(n) is the number of coverings of 1..n by cyclic words of length n, such that each value from 1 to n appears precisely 3 times. That is, the union of all the letters in all of the words of a given covering is the multiset {1,1,1,2,2,2,...,n,n,n}. Repeats of words are not allowed in a given covering.

Table of values

n a(n)
0 1
1 1
2 2
3 12
4 192
5 5744
6 260904
7 16542648
8 1395722688
9 151232990208
10 20468918305536
11 3384387717897216
12 671260382408564352
13 157302245641224362112
14 42996605332700377396992
15 13558408172347636250832384
16 4885584146166061652811300864
17 1994958243661170192648338792448

List of values

[1, 1, 2, 12, 192, 5744, 260904, 16542648, 1395722688, 151232990208, 20468918305536, 3384387717897216, 671260382408564352, 157302245641224362112, 42996605332700377396992, 13558408172347636250832384, 4885584146166061652811300864, 1994958243661170192648338792448]

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

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