OFFSET
1,4
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+4k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>4k AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+4k<=n, j+5k<=n, m+k<=n
LINKS
V. Kotesovec, Number of ways of placing non-attacking queens, kings, bishops and knights (in English and Czech)
Wikipedia, Fairy chess piece
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved