Covering $6 \times 6$ chessboard with $1 \times 2$ tiles
113418
Minimum number of dominoes on an $n \times n$ chessboard to prevent placement of another domino.
111609
Each $2\times 5$ rectangle contains $1\times 3$ rectangle
81928
Covering with most possible equal size subsets having pairwise singleton intersections
154494
Prove that there exists a row or a column of the chessboard which contains at least √n distinct numbers.
28843
Algorithm for finding the fewest rectangles to cover a set of rectangles without overlapping
5448
Finding the closure of some subsets of the ordered square
52564
$m\times n$ matrix with an even number of 1s in each row and column
102429
There are 2 groups of order 6 (up to isomorphism)
78163
Hint for problem on $4 \times 7$-chessboard problem related to pigeonhole principle
44852
How to make a resizable chess board?
141101
Russia (2000) contest:Prove the existence of a pair of rows and columns with intersections differently coloured
111035
Chess Master Problem
123710
Find eight elements in $S_6$ that commute with $(12)(34)(56)$
18482
Can the squares with side $1/n$ be packed into a $1 \times \zeta(2)$ rectangle?
43845
Partitioning the edges of $K_n$ into $\lfloor \frac n6 \rfloor$ planar subgraphs
157079
Maximal cardinality of a family of pairwise disjoint "figure eights" in the plane
97627
filling an occluded plane with the smallest number of rectangles