A190394 Maximum number of nonattacking nightriders on an n X n board.
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, 93
Offset: 1
Examples
From _Rob Pratt_, Jul 24 2015: (Start) 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 (End)
Links
- Andy Huchala, Python program.
- Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, pp. 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
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
a(33) from Andy Huchala, Mar 30 2024
Comments