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.

1, 1, 2, 6, 24, 120, 392, 1810, 10400, 72228, 589674, 5196870, 52398658, 588036216, 7274466172, 98024173852, 1427556373892

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[2,5] 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, A189564, A189565, A189566.

Formula

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