OFFSET
1,2
COMMENTS
In fairy chess, the rider [1,4] is called a Girafferider.
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>k for all i>=1, j>=1, k>=1, i+k<=n, j+4k<=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