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A352623 a(n) is the maximum number k of queens that can be placed on an n X n chessboard such that, for each number j in 0..k-1, there is a queen attacking exactly j unoccupied squares. 0

%I #52 Apr 10 2022 10:04:12

%S 0,1,0,5,8,11,14,18,22

%N a(n) is the maximum number k of queens that can be placed on an n X n chessboard such that, for each number j in 0..k-1, there is a queen attacking exactly j unoccupied squares.

%C On the 6 X 6 board in the illustration (see Example), each square containing a number is occupied by a queen, and the number in that square is the number of unoccupied squares attacked by that queen. (Each square with no number is unoccupied.)

%C Solvers:

%C a(4) = 8 by Rodolfo Kurchan

%C a(5) = 11 by Gustavo PiƱeiro

%C a(6) = 14 by Antonio Misericordia

%C a(7) = 18 by Antonio Misericordia

%C a(8) = 22 by Giorgio Vecchi

%H Rodolfo Kurchan, <a href="https://www.puzzlefun.online/chess-puzzle-fun-05">Chess Puzzle Fun 5 Uneven Attacks</a>

%e Solution illustrating a(6) = 14 by Antonio Misericordia:

%e +---+---+---+---+---+---+

%e | 2 | 7 | | 5 | 4 | 0 |

%e +---+---+---+---+---+---+

%e | 10| | | | 6 | 1 |

%e +---+---+---+---+---+---+

%e | | | | 11| | 3 |

%e +---+---+---+---+---+---+

%e | | | | 13| | 8 |

%e +---+---+---+---+---+---+

%e | | | | | | |

%e +---+---+---+---+---+---+

%e | | | 12| | 9 | |

%e +---+---+---+---+---+---+

%Y Cf. A186238.

%K nonn,more

%O 0,4

%A _Rodolfo Kurchan_, Mar 24 2022

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Last modified June 20 16:01 EDT 2024. Contains 373526 sequences. (Running on oeis4.)