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A190394 Maximum number of nonattacking nightriders on an n X n board.

%I A190394 #47 Apr 02 2024 03:46:50
%S A190394 1,4,5,8,10,16,17,20,21,24,26,32,33,36,39,42,45,48,51,54,58,64,65,66,
%T A190394 68,72,75,80,81,84,87,90,93
%N A190394 Maximum number of nonattacking nightriders on an n X n board.
%C A190394 A nightrider is a fairy chess piece that can move any distance in a direction specified by a knight move.
%C A190394 Maximum number of nonattacking nightriders on an n X n toroidal board is n.
%H A190394 Andy Huchala, <a href="/A190394/a190394.py.txt">Python program</a>.
%H A190394 Vaclav Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>, 6ed, 2013, pp. 751-763.
%H A190394 Rob Pratt, <a href="/A190394/a190394.pdf">54 nonattacking nightriders on a 20 X 20 board</a>.
%F A190394 2n <= a(n) <= 3n-2, for n > 3.
%F A190394 a(n) >= 24*floor((n+4)/10)-8, for n >= 6. - _Vaclav Kotesovec_, Apr 01 2012
%e A190394 From _Rob Pratt_, Jul 24 2015: (Start)
%e A190394 a(20) = 54:
%e A190394   XX--XXXX---X------XX
%e A190394   XX---------X--XX--XX
%e A190394   --------------------
%e A190394   ---X----------------
%e A190394   X-----------------X-
%e A190394   X-----------------X-
%e A190394   X-------------------
%e A190394   X---------X---------
%e A190394   ------------------XX
%e A190394   ------------X-------
%e A190394   -------X------------
%e A190394   XX------------------
%e A190394   ---------X---------X
%e A190394   -------------------X
%e A190394   -X-----------------X
%e A190394   -X-----------------X
%e A190394   ----------------X---
%e A190394   --------------------
%e A190394   XX--XX--X---------XX
%e A190394   XX------X---XXXX--XX
%e A190394 (End)
%Y A190394 Cf. A085801, A190393, A172141, A173429.
%K A190394 nonn,nice,hard,more
%O A190394 1,2
%A A190394 _Vaclav Kotesovec_, May 10 2011
%E A190394 Terms a(11)-a(16) from _Vaclav Kotesovec_, May 13 2011
%E A190394 Terms a(17)-a(19) from _Vaclav Kotesovec_, Apr 01 2012
%E A190394 a(20) from _Rob Pratt_, Jul 24 2015
%E A190394 a(21)-a(32) from _Paul Tabatabai_, Nov 06 2018
%E A190394 a(33) from _Andy Huchala_, Mar 30 2024