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Number of ways to place n nonattacking composite pieces rook + semi-rider[6,6] on an n X n chessboard.
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%I #6 Sep 12 2015 11:00:25

%S 1,2,6,24,120,720,4920,37488,319644,3033264,31784280,364902480,

%T 4509620040,59768680032,847746532152

%N Number of ways to place n nonattacking composite pieces rook + semi-rider[6,6] on an n X n chessboard.

%C a(n) is also number of permutations p of 1,2,...,n satisfying p(j+6k)-p(j)<>6k for all j>=1, k>=1, j+6k<=n

%C For information about semi-pieces see semi-bishop (A187235) and semi-queen (A099152).

%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. A189285, A099152, A189843, A189844, A189846, A189847, A189842, A187235

%K nonn,hard

%O 1,2

%A _Vaclav Kotesovec_, Apr 29 2011