On equivalence of negaperiodic Golay pairs

Associated pairs as defined by Ito (J Algebra 234:651-663, 2000) are pairs of binary sequence of length 2t satisfying certain autocorrelation properties that may be used to construct Hadamard matrices of order 4t. More recently, Balonin and Dokovic (Inf Control Syst 5:217, 2015) use the term negaperiodic Golay pairs. We define extended negaperiodic Golay pairs and prove a one-to-one correspondence with central relative (4t, 2, 4t, 2t)-difference sets in dicyclic groups of order 8t. We present a new approach for computing negaperiodic Golay pairs up to equivalence, and determine conditions where equivalent pairs correspond to equivalent Hadamard matrices. We complete an enumeration of negaperiodic Golay pairs of length 2t for 1 <= t <= 10, and sort them into equivalence classes. Some structural properties of negaperiodic Golay pairs are derived.