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