3 problems

A negacyclic C-matrix is a negacyclic matrix with entries in $\{0,\pm1\}$ satisfying the C-matrix weighing condition. Negacyclic C-matrix nonexistence conjecture. There are no nega…

A Hadamard matrix of 2N-type is a Hadamard matrix of order $2v$ of the block form … where $A$ and $B$ are negacyclic blocks. 2N-type existence conjecture. For each even integer…

A negacyclic Hadamard matrix is a Hadamard matrix whose rows are generated from one another by negacyclic shifts. Negacyclic Hadamard nonexistence conjecture. There are no negacycl…