|
|
A189878
|
|
Number of ways to place n nonattacking composite pieces queen + rider[2,5] on an n X n chessboard.
|
|
2
|
|
|
1, 0, 0, 2, 10, 4, 28, 20, 56, 72, 200, 644, 2940, 9152, 39200, 166100, 739924, 3586840, 18640500, 107580592, 547737844, 3080550788
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,4
|
|
COMMENTS
|
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>2k AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2k<=n, j+5k<=n, m+k<=n
|
|
LINKS
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,hard
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|