A189838 Number of ways to place n nonattacking composite pieces rook + rider[2,2] on an n X n chessboard.

1, 2, 4, 16, 36, 128, 672, 4264, 25044, 173712, 1318904, 11069056, 96808692, 927478976, 9435033872, 103783608480, 1195155968388

Offset

1,2

Comments

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

Links

Table of n, a(n) for n=1..17.

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

Wikipedia, Fairy chess piece

Crossrefs

Cf. A110128, A000170

Sequence in context: A101926 A087965 A074411 * A247219 A265835 A185074

Adjacent sequences: A189835 A189836 A189837 * A189839 A189840 A189841

Keyword

nonn,hard

Author

Vaclav Kotesovec, Apr 29 2011

Status

approved