

A189837


Number of ways to place n nonattacking composite pieces rook + rider[1,2] on an n X n chessboard.


6



1, 2, 2, 8, 12, 22, 58, 276, 648, 2304, 6508, 24528, 96402, 466922, 2271738, 13723826, 76579326, 512425626, 3281233020, 24654941268, 175398054696
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

(in fairy chess the rider [1,2] is called a Nightrider, Rook + Nightrider = Waran)
a(n) is also number of permutations p of 1,2,...,n satisfying p(i+k)p(i)<>2k AND p(j+2k)p(j)<>k for all i>=1, j>=1, k>=1, i+k<=n, j+2k<=n


LINKS

Table of n, a(n) for n=1..21.
V. Kotesovec, Number of ways of placing nonattacking queens, kings, bishops and knights (in English and Czech)
Wikipedia, Fairy chess piece


CROSSREFS

Cf. A102388, A000170
Sequence in context: A008828 A254219 A053414 * A274409 A302118 A014236
Adjacent sequences: A189834 A189835 A189836 * A189838 A189839 A189840


KEYWORD

nonn,hard


AUTHOR

Vaclav Kotesovec, Apr 29 2011


STATUS

approved



