A189861 - OEIS

A189861

Number of ways to place n nonattacking composite pieces rook + rider[4,5] on an n X n chessboard.

%I #6 Sep 12 2015 11:00:25

%S 1,2,6,24,120,552,2826,17080,117816,943250,7369128,63533572,603300392,

%T 6280101222,71927971040,836503868762

%N Number of ways to place n nonattacking composite pieces rook + rider[4,5] on an n X n chessboard.

%C 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 for all i>=1, j>=1, k>=1, i+4k<=n, j+5k<=n

%H V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Number of ways of placing non-attacking queens, kings, bishops and knights</a> (in English and Czech)

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a>

%Y Cf. A000170, A189852, A189856, A189859

%K nonn,hard

%O 1,2

%A _Vaclav Kotesovec_, Apr 29 2011