N denotes a minimum number of bishops to guarantee full coverage of a standard chessboard.
How much is
N, and where should
these bishops be placed?
To cover a square means either to stay on it or to attack it.
(In reply to
A different count by Jer)
Actually, your 4x5 patch is also an over-constraint. Consider bishops placed: b1, e2, d5, d7, for example. b1 is off the patch, but they do the trick.
There are 24 of these solutions having one of the four bishops sitting outside the 4x5 patch. I have marked them on my previous list of 108 solutions with "***" and they bring the total to 108.
re: A different count
