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.

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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.

A245011 Number of ways to place n nonattacking princesses on an n X n board.

Original entry on oeis.org

1, 4, 6, 86, 854, 9556, 146168, 2660326, 56083228, 1349544632, 36786865968, 1117327217782
Offset: 1

Views

Author

Vaclav Kotesovec, Sep 16 2014

Keywords

Comments

A princess moves like a bishop and a knight.

Links

Crossrefs

Cf. A201513, A000170, A002465, A201540.
Cf. A185085, A051223, A244284, A201511, A201861, A137774.
Cf. A225555.
Previous Showing 11-12 of 12 results.

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

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