

A189876


Number of ways to place n nonattacking composite pieces queen + rider[2,3] on an n X n chessboard.


2



1, 0, 0, 2, 10, 0, 0, 0, 0, 16, 60, 40, 304, 620, 2512, 8734, 28410, 94312, 345824, 1391072, 5759566, 25227796, 121663032, 635977968
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OFFSET

1,4


COMMENTS

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


LINKS



CROSSREFS



KEYWORD

nonn,hard


AUTHOR



STATUS

approved



