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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 Table of n, a(n) for n=1..32. V. Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 751-763. Rob Pratt, 54 nonattacking nightriders on a 20 X 20 board 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 Cf. A085801, A190393, A172141, A173429. Sequence in context: A139132 A295068 A022435 * A116050 A241413 A056721 Adjacent sequences: A190391 A190392 A190393 * A190395 A190396 A190397 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.)