cp's OEIS Frontend

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.

Showing 1-2 of 2 results.

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.

Original entry on oeis.org

1, 1, 0, 0, 4, 4, 10, 24, 252, 410, 1998, 7798, 65188, 280582, 2281108, 10585748, 110903088
Offset: 0

Views

Author

Alois P. Heinz, Dec 06 2018

Keywords

Comments

a(n) is even for n > 1.

Examples

			a(1) = 1: 111.
a(4) = 4: 111224234343, 111343432422, 224234343111, 343432422111.

Links

Crossrefs

Cf. A285527, A322153.

A321956 Number of permutations of 3 indistinguishable copies of 1,...,n such that the first and second copies of j are adjacent and there are exactly j-1 numbers between the second and the third copy of j.

Original entry on oeis.org

1, 1, 0, 2, 4, 0, 16, 40, 0, 456, 1759, 0, 34636, 175198, 0, 5494621, 34043062, 0
Offset: 0

Views

Author

Alois P. Heinz, Nov 22 2018

Keywords

Examples

			a(3) = 2: 111332232, 332232111.
a(4) = 4: 111334432242, 332232441114, 334432242111, 441114332232.

Links

Crossrefs

Cf. A264813, A322153.

Formula

a(n) = 0 for n == 2 (mod 3).
Showing 1-2 of 2 results.

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

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