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A190394 Maximum number of nonattacking nightriders on an n X n board. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
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.
LINKS
V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 751-763.
FORMULA
2n <= a(n) <= 3n-2, for n>3.
a(n) >= 24*floor((n+4)/10)-8, for n>=6. - Vaclav Kotesovec, Apr 01 2012
EXAMPLE
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
CROSSREFS
Sequence in context: A139132 A295068 A022435 * A116050 A241413 A056721
KEYWORD
nonn,nice,hard,more
AUTHOR
Vaclav Kotesovec, May 10 2011
EXTENSIONS
Terms a(11)-a(16) from Vaclav Kotesovec, May 13 2011
Terms a(17)-a(19) from Vaclav Kotesovec, Apr 01 2012
a(20) from Rob Pratt, Jul 24 2015
a(21)-a(32) from Paul Tabatabai, Nov 06 2018
STATUS
approved

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Last modified February 24 04:32 EST 2024. Contains 370288 sequences. (Running on oeis4.)