Almost completely coloring a chessboard
Source: XVIII Cono Sur Mathematical Olympiad (2007)
August 10, 2011
combinatorics
Problem Statement
Some cells of a table are colored. The table is charrua if none of the rows and none of the columns are completely colored.(a) What is the maximum number of colored cells that a charrua table can have?
(b) For such , calculate the number of distinct charrua tables that exist.