1,2

Abstract: Strongly quadrangular matrices have been introduced in the study of the combinatorial properties of unitary matrices. It is known that if a (0, 1)-matrix supports a unitary then it is strongly quadrangular. However the converse is not necessarily true. In this paper, we fully classify strongly quadrangular matrices up to degree 5. We prove that the smallest strongly quadrangular matrices which do not support unitaries have exactly degree 5. Further, we isolate two submatrices not allowing a (0, 1)-matrix to support unitaries.

Simone Severini and Ferenc Szollosi, A further look into combinatorial orthogonality

Sequence in context: A112281 A014517 A020110 this_sequence A020134 A120490 A003514

Adjacent sequences: A140833 A140834 A140835 this_sequence A140837 A140838 A140839

nonn

Jonathan Vos Post (jvospost3(AT)gmail.com), Jul 18 2008