

A189873


Number of ways to place n nonattacking composite pieces queen + rider[1,3] on an n X n chessboard.


3



1, 0, 0, 0, 0, 0, 0, 0, 0, 4, 56, 18, 116, 112, 408, 916, 2400, 7228, 27368, 111478, 445644, 1674860, 7624368, 38737270, 178933064
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OFFSET

1,10


COMMENTS

In fairy chess, the rider [1,3] is called a Camelrider.
a(n) is also number of permutations p of 1,2,...,n satisfying p(i+k)p(i)<>3k AND p(j+3k)p(j)<>k AND p(m+k)p(m)<>k for all i>=1, j>=1, m>=1, k>=1, i+k<=n, j+3k<=n, m+k<=n


LINKS



CROSSREFS



KEYWORD

nonn,hard


AUTHOR



STATUS

approved



