A322180 - OEIS

A322180

The number of permutations of {1,2,...,n,1,2,...,n} with the property that there are k or fewer numbers between the two k's in the set for k=1,...,n.

1, 1, 5, 36, 466, 8942, 240366, 8576860, 392952468, 22470271108, 1568892808268, 131334875308512, 12984315462058432, 1496760634095487312, 198986563111871018384, 30220934753050481089120, 5199918150481843712777536, 1006247909956375968130135968, 217571773636594227310460491488

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OFFSET

0,3

LINKS

Table of n, a(n) for n=0..18.

EXAMPLE

In case of n = 2.

| permutation

--+-------------

1 | [1, 1, 2, 2]

2 | [1, 2, 1, 2]

3 | [2, 1, 1, 2]