Can anyone tell me an example of a matroid of rank 5 or higher which is not a product of two lower rank matroids and is not the independence matroid of a finite set of vectors in a vector space over any field?
Can anyone tell me an example of a matroid of rank 5 or higher which is not a product of two lower rank matroids and is not the independence matroid of a finite set of vectors in a vector space over any field?