A189564 Number of permutations p of 1,2,...,n satisfying |p(i+1)-p(i)|<>5 and |p(j+5)-p(j)|<>1 for all i=1..n-1, j=1..n-5.

1, 1, 2, 6, 24, 120, 336, 1474, 8340, 57756, 475658, 4171070, 41950294, 472535256, 5882635676, 79963449714, 1173614446044

Offset: 0

Author

Vaclav Kotesovec, Apr 23 2011

Keywords

• nonn
• more
• hard

Comments

a(n) is also the number of ways to place n nonattacking pieces rook + leaper[1,5] on an n X n chessboard.

Links

• V. Kotesovec, Number of ways of placing non-attacking queens, kings, bishops and knights (in English and Czech)

Crossrefs

Cf. A137774, A189358, A189563.

Formula

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