|
|
A189852
|
|
Number of ways to place n nonattacking composite pieces rook + rider[1,5] on an n X n chessboard.
|
|
4
|
|
|
1, 2, 6, 24, 120, 336, 1474, 8340, 57756, 475658, 2812910, 20852460, 181255892, 1817101242, 20435345782, 197871434994
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>k for all i>=1, j>=1, k>=1, i+k<=n, j+5k<=n
|
|
LINKS
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,hard
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|