A189856 Number of ways to place n nonattacking composite pieces rook + rider[2,5] on an n X n chessboard.

1, 2, 6, 24, 120, 392, 1810, 10400, 72228, 589674, 3823906, 29420944, 266232984, 2711139976, 30669073348, 316482938974

Offset

1,2

Comments

a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>2k for all i>=1, j>=1, k>=1, i+2k<=n, j+5k<=n

Links

Table of n, a(n) for n=1..16.

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

Wikipedia, Fairy chess piece

Crossrefs

Cf. A000170, A189854, A189855

Sequence in context: A355988 A330043 A062348 * A189567 A189859 A189569

Adjacent sequences: A189853 A189854 A189855 * A189857 A189858 A189859

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved