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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.

A320392 Number of permutations of 3 indistinguishable copies of 1,...,n such that there are exactly j numbers between the first and the third copy of j and floor(j/2) numbers between the first and the second or between the second and the third copy of j.

Table of values

n a(n)
0 1
1 1
2 0
3 0
4 4
5 4
6 10
7 24
8 252
9 410
10 1998
11 7798
12 65188
13 280582
14 2281108
15 10585748
16 110903088

List of values

[1, 1, 0, 0, 4, 4, 10, 24, 252, 410, 1998, 7798, 65188, 280582, 2281108, 10585748, 110903088]

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

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