

A189851


Number of ways to place n nonattacking composite pieces rook + rider[1,4] on an n X n chessboard.


5



1, 2, 6, 24, 48, 182, 868, 5752, 22952, 131766, 912964, 7556978, 52602390, 432795244, 4121203656, 44335718598, 416447624724
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OFFSET

1,2


COMMENTS

In fairy chess, the rider [1,4] is called a Girafferider.
a(n) is also number of permutations p of 1,2,...,n satisfying p(i+k)p(i)<>4k AND p(j+4k)p(j)<>k for all i>=1, j>=1, k>=1, i+k<=n, j+4k<=n


LINKS

Table of n, a(n) for n=1..17.
V. Kotesovec, Number of ways of placing nonattacking queens, kings, bishops and knights (in English and Czech)
Wikipedia, Fairy chess piece


CROSSREFS

Cf. A000170, A189837, A189850
Sequence in context: A092485 A113904 A099144 * A189563 A321613 A104114
Adjacent sequences: A189848 A189849 A189850 * A189852 A189853 A189854


KEYWORD

nonn,hard


AUTHOR

Vaclav Kotesovec, Apr 29 2011


STATUS

approved



