I was thinking about something like this the other day (though the board is 5x5 and the middle space is a "free" space that everyone gets, well, for free). Except my question was, what is the largest number of cards that can be generated such that no two people can win at once? (The Rules in short: the "B" column contains 5 of the numbers 1-15 in any order, "I" contains 16-30, etc. (but the "N" column only has 4 numbers since the middle is a free space), numbers are called out one at a time, and you win when you get 5 in a row horizontally, vertically, or diagonally).