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: A133806 A005176 A050335 this_sequence A019681 A054529 A074934

Adjacent sequences: A140857 A140858 A140859 this_sequence A140861 A140862 A140863

nonn

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