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Recently the author and Kimura have considered a construction of doubly-even codes from a given doubly-even code. In this note, we show that the restricutoion of doubly-even can be removed in the above construction. As an application, at least 137 ...

We classify extremal Hermitian self-dual quaternary codes of lengths 30 and 32 with an automorphism of odd prime order. We prove that there exists exactly one extremal Hermitian self-dual $[{30,15,12}]$ quaternary code with a nontrivial automorphism of ...

Let C be a binary extremal self-dual code of length n ≥ 48. We prove that for each σ ∈ Aut(C) of prime order p ≥ 5 the number of fixed points in the permutation action on the coordinate positions is bounded by the number of p-cycles. It turns out that ...