|
|
A189858
|
|
Number of ways to place n nonattacking composite pieces rook + rider[3,4] on an n X n chessboard.
|
|
1
|
|
|
1, 2, 6, 24, 80, 326, 1566, 9544, 53696, 347382, 2566892, 21907934, 184868860, 1704360992, 17294597926, 192725663600, 2139133978996
(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+3k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>3k for all i>=1, j>=1, k>=1, i+3k<=n, j+4k<=n.
|
|
LINKS
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,hard
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|