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 1-6 of 6 results.

A189566 Number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>4 and |p(j+4)-p(j)|<>2 for all i=1..n-2, j=1..n-4.

Original entry on oeis.org

1, 2, 6, 24, 60, 208, 1184, 7840, 51636, 410272, 3836456, 39971896, 455888312, 5717233896, 78164908748, 1153568477544, 18263732340736, 308795344195456, 5550690255143992, 105653899427070440, 2122307518838927952
Offset: 1

Views

Author

Vaclav Kotesovec, Apr 23 2011

Keywords

Comments

a(n) is also the number of ways to place n nonattacking pieces rook + leaper[2,4] on an n X n chessboard.

Links

Crossrefs

Cf. A137774, A189358, A189563, A189564, A189565.

Formula

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

Extensions

a(17)-a(21) from Max Alekseyev, Jul 28 2024

A189567 Number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>5 and |p(j+5)-p(j)|<>2 for all i=1..n-2, j=1..n-5.

Original entry on oeis.org

1, 1, 2, 6, 24, 120, 392, 1810, 10400, 72228, 589674, 5196870, 52398658, 588036216, 7274466172, 98024173852, 1427556373892
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[2,5] on an n X n chessboard.

Links

Crossrefs

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

Formula

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

A189568 Number of permutations p of 1,2,...,n satisfying |p(i+3)-p(i)|<>4 and |p(j+4)-p(j)|<>3 for all i=1..n-3, j=1..n-4.

Original entry on oeis.org

1, 1, 2, 6, 24, 80, 326, 1566, 9544, 65036, 518498, 4750006, 48830634, 554929274, 6926227324, 93970452970, 1377573324202
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[3,4] on an n X n chessboard.

Links

Crossrefs

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

Formula

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

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.

A189867 Number of ways to place n nonattacking composite pieces queen + leaper[2,3] on an n X n chessboard.

Original entry on oeis.org

1, 0, 0, 2, 10, 0, 0, 0, 0, 48, 152, 472, 2696, 12320, 74436, 429620, 2515116, 16122496, 113016608, 843492920, 6575649316, 54694203188
Offset: 1

Views

Author

Vaclav Kotesovec, Apr 29 2011

Keywords

Comments

In fairy chess the leaper [2,3] is called a zebra.
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>3 AND |p(j+3)-p(j)|<>2 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2<=n, j+3<=n, m+k<=n

Links

Crossrefs

Cf. A051223, A189864, A189565

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.
Showing 1-6 of 6 results.

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

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