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Cocyclic Hadamard matrices over $${\mathbf Z}_ t\times {\mathbf Z}_ 2^ 2$$. (English) Zbl 0838.05017
From the authors’ abstract: A natural starting point in a systematic search for cocyclic Hadamard matrices is the study of the case of cocycles over the groups $$Z_t\times Z^2_2$$, for $$t$$ odd. The solution set includes all Williamson Hadamard matrices, so this set of groups is potentially a uniform source for generation of Hadamard matrices. We present our analytical and computational results.

##### MSC:
 05B20 Combinatorial aspects of matrices (incidence, Hadamard, etc.) 05B99 Designs and configurations