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A190394
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Maximum number of nonattacking nightriders on an n X n board.
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3
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1, 4, 5, 8, 10, 16, 17, 20, 21, 24, 26, 32, 33, 36, 39, 42, 45, 48, 51, 54, 58, 64, 65, 66, 68, 72, 75, 80, 81, 84, 87, 90
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OFFSET
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1,2
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COMMENTS
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A nightrider is a fairy chess piece that can move any distance in a direction specified by a knight move.
Maximum number of nonattacking nightriders on an n X n toroidal board is n.
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LINKS
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FORMULA
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2n <= a(n) <= 3n-2, for n>3.
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EXAMPLE
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a(20) = 54:
XX--XXXX---X------XX
XX---------X--XX--XX
--------------------
---X----------------
X-----------------X-
X-----------------X-
X-------------------
X---------X---------
------------------XX
------------X-------
-------X------------
XX------------------
---------X---------X
-------------------X
-X-----------------X
-X-----------------X
----------------X---
--------------------
XX--XX--X---------XX
XX------X---XXXX--XX - Rob Pratt, Jul 24 2015
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CROSSREFS
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KEYWORD
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nonn,nice,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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