This problem is related to the 17x17 challenge. Given a matrix filled with ones and zeros, determine whether or not any rectangles are present. A rectangle is a formed whenever four ones appear in the corners of a rectangular region of the matrix.

Examples:

 Input  a = [ 1 0 0 0 0
              0 0 0 1 0
              0 0 0 0 1
              0 0 0 0 1
              0 0 1 0 0 ]
 Output tf is false

You can't form any rectangles here.

 Input  a = [ 1 0 1 0
              0 0 1 0
              1 0 1 0
              0 0 1 1 ]
 Output tf is true

There is a rectangle: a([1 3],[1 3]) is [1 1; 1 1]