(en.wikipedia.org) Eight queens puzzle - Wikipedia

ROAM_REFS: https://en.wikipedia.org/wiki/Eight_queens_puzzle

The eight queens puzzle is the problem of placing eight chess queens on an 8×8 chessboard so that no two queens threaten each other; thus, a solution requires that no two queens share the same row, column, or diagonal. There are 92 solutions. The problem was first posed in the mid-19th century. In the modern era, it is often used as an example problem for various computer programming techniques.

The eight queens puzzle is a special case of the more general n queens problem of placing n non-attacking queens on an n/×/n chessboard. Solutions exist for all natural numbers n with the exception of n = 2 and n = 3. Although the exact number of solutions is only known for n ≤ 27, the asymptotic growth rate of the number of solutions is approximately (0.143 n)ⁿ.