For my discrete mathematics class an exercise is to look at the following square and use it to construct a 2-(16,6,2) design:
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
So far my only inspiration has been to look at the amount of blocks b of our design, which should be 16 by the formula b = lambda (v choose t)/(k choose t) , but i don't know how to continue