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  2. Mathematical chess problem - Wikipedia

    en.wikipedia.org/wiki/Mathematical_chess_problem

    Problems are further extended by asking how many possible solutions exist. Further generalizations apply the problem to NxN boards. [3] [4] An 8×8 chessboard can have 16 independent kings, 8 independent queens, 8 independent rooks, 14 independent bishops, or 32 independent knights. [5] Solutions for kings, bishops, queens and knights are shown ...

  3. Rook polynomial - Wikipedia

    en.wikipedia.org/wiki/Rook_polynomial

    The board is the ordinary chessboard if all squares are allowed and m = n = 8 and a chessboard of any size if all squares are allowed and m = n. The coefficient of x k in the rook polynomial R B (x) is the number of ways k rooks, none of which attacks another, can be arranged in the squares of B. The rooks are arranged in such a way that there ...

  4. Graph coloring - Wikipedia

    en.wikipedia.org/wiki/Graph_coloring

    With only two colors, it cannot be colored at all. With four colors, it can be colored in 24 + 4 × 12 = 72 ways: using all four colors, there are 4! = 24 valid colorings (every assignment of four colors to any 4-vertex graph is a proper coloring); and for every choice of three of the four colors, there are 12 valid 3-colorings. So, for the ...

  5. Polyomino - Wikipedia

    en.wikipedia.org/wiki/Polyomino

    The simplest implementation involves adding one square at a time. Beginning with an initial square, number the adjacent squares, clockwise from the top, 1, 2, 3, and 4. Now pick a number between 1 and 4, and add a square at that location. Number the unnumbered adjacent squares, starting with 5.

  6. MacMahon Squares - Wikipedia

    en.wikipedia.org/wiki/MacMahon_Squares

    The goal is to arrange the squares into a 4 by 6 grid so that when two squares share an edge, the common edge is the same color in both squares. In 1964, a supercomputer was used to produce 12,261 solutions to the basic version of the MacMahon Squares puzzle, with a runtime of about 40 hours. [2]

  7. Eight queens puzzle - Wikipedia

    en.wikipedia.org/wiki/Eight_queens_puzzle

    If the remainder is 3, move 2 to the end of even list and 1,3 to the end of odd list (4, 6, 8, 2 – 5, 7, 9, 1, 3). Append odd list to the even list and place queens in the rows given by these numbers, from left to right (a2, b4, c6, d8, e3, f1, g7, h5).

  8. Hilbert's seventeenth problem - Wikipedia

    en.wikipedia.org/wiki/Hilbert's_seventeenth_problem

    A result of Albrecht Pfister [8] shows that a positive semidefinite form in n variables can be expressed as a sum of 2 n squares. [9] Dubois showed in 1967 that the answer is negative in general for ordered fields. [10] In this case one can say that a positive polynomial is a sum of weighted squares of rational functions with positive ...

  9. Mutilated chessboard problem - Wikipedia

    en.wikipedia.org/wiki/Mutilated_chessboard_problem

    A domino placed on the chessboard will always cover one white square and one black square. Therefore, any collection of dominoes placed on the board will cover equal numbers of squares of each color. But any two opposite squares have the same color: both black or both white. If they are removed, there will be fewer squares of that color and ...