Ken's POTW
NonAgressive Queens

Can you place N queens on an NxN chessboard such that no queen is
attacking any other? Can you find solutions for N <= 7? How
many?

Consider a hexagon with a sidelength of 3. Each side is marked off
at unit intervals, then lines are drawn parallel to the sides to
connect these unit marks. This results in 6 rows of triangles in
each of the three directions. Assuming now that queens can move
in any of the three directions, how many queens can be placed, one
per triangle, such that no queen attacks any other?

Consider a triangle with a sidelength of 9. Each side is marked off
at unit intervals, then lines are drawn parallel to the sides to
connect these unit marks. (This looks basically like the hexagon
with its sides extended.) This results in 9 rows of triangles in
each of the three directions. Now, how many of the 3directional
queens can be placed, one per triangle, such that no queen attacks
any other?
Source: 1. Many sources. 2,3. Original.
Solution
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