1,4

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: A094877 A006560 A088251 this_sequence A127528 A063070 A049802

Adjacent sequences: A140836 A140837 A140838 this_sequence A140840 A140841 A140842

nonn

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