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 1-3 of 3 results.

A189569 Number of permutations p of 1,2,...,n satisfying |p(i+3)-p(i)|<>5 and |p(j+5)-p(j)|<>3 for all i=1..n-3, j=1..n-5.

Original entry on oeis.org

1, 1, 2, 6, 24, 120, 464, 2274, 13236, 91760, 740562, 6541984, 65632694, 732880076, 8995905626, 120367234946
Offset: 0

Views

Author

Vaclav Kotesovec, Apr 23 2011

Keywords

Comments

a(n) is also the number of ways to place n nonattacking pieces rook + leaper[3,5] on an n X n chessboard.

Links

Crossrefs

Cf. A137774, A189358, A189563, A189564, A189565, A189566, A189567, A189568.

Formula

Asymptotic: a(n)/n! ~ 1/e^4.

A189570 Number of permutations p of 1,2,...,n satisfying |p(i+4)-p(i)|<>5 and |p(j+5)-p(j)|<>4 for all i=1..n-4, j=1..n-5.

Original entry on oeis.org

1, 1, 2, 6, 24, 120, 552, 2826, 17080, 117816, 943250, 8330356, 82954582, 915854808, 11147075946, 147948526182
Offset: 0

Views

Author

Vaclav Kotesovec, Apr 23 2011

Keywords

Comments

a(n) is also the number of ways to place n nonattacking pieces rook + leaper[4,5] on an n X n chessboard.

Links

Crossrefs

Cf. A137774, A189358, A189563, A189564, A189565, A189566, A189567, A189568, A189569.

Formula

Asymptotic: a(n)/n! ~ 1/e^4.

A189870 Number of ways to place n nonattacking composite pieces queen + leaper[3,4] on an n X n chessboard.

Original entry on oeis.org

1, 0, 0, 2, 2, 4, 28, 0, 20, 52, 280, 1192, 5520, 20196, 115936, 701836, 4174032, 27261284, 193428616, 1445733328, 11133210948
Offset: 1

Views

Author

Vaclav Kotesovec, Apr 29 2011

Keywords

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+3)-p(i)|<>4 AND |p(j+4)-p(j)|<>3 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+3<=n, j+4<=n, m+k<=n

Links

Crossrefs

Cf. A051223, A189865, A189868, A189568
Showing 1-3 of 3 results.

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

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