The problem of determining how many non-attacking chess
kings, K(n), can be placed on an n × n
chessboard. For n = 8, the solution is 16. The general solution
is K(n) = ¼n 2 if n
is even and K(n) = ¼(n + 1) 2
if n is odd. The minimum number of kings needed to attack or occupy
all squares on an 8 × 8 chessboard is nine.