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Number of ways to place n nonattacking composite pieces rook + semi-rider[2,2] on an n X n chessboard.
4

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

%S 1,2,5,18,71,356,2097,14212,105821,887576,8093601,81310936,876456695,

%T 10257217440,127631146697,1705775408656

%N Number of ways to place n nonattacking composite pieces rook + semi-rider[2,2] on an n X n chessboard.

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

%C 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. A189281, A099152, A189838, A187235

%K nonn,hard

%O 1,2

%A _Vaclav Kotesovec_, Apr 29 2011