Avoiding Colinear Points

[Jud McCranie]

At 07:09 PM 10/21/2004, Kennedy wrote:
>There is no solution to the n-queens problem for n=2 or n=3.
>Besides, superimposing two n-queens solutions does not always yield 2n points.
>For example, here are two 8-queens solutions and their superposition, 
>which only has 13 distinct points.

OK.  Martin Gardner covered this in one of his articles in Scientific 
American.  I just located it in "Penrose Tiles to Trapdoor Ciphers", 
chapter 5, this problem starts on page 69.  He gives examples of 2n 
solutions for 2 <= n <= 16. At the beginning he says that it is unknown if 
2n is always possible, but I need to read on...