Construction of extremal Type II ℤ_2k-codes
We give methods for constructing many self-dual ℤ_m-codes and Type II ℤ_2k-codes of length 2n starting from a given self-dual ℤ_m-code and Type II ℤ_2k-code of length 2n, respectively. As an application, we construct extremal Type II ℤ_2k-codes of length 24 for k=4,5,…,20 and extremal Type II ℤ_2k-codes of length 32 for k=4,5,…,10. We also construct new extremal Type II ℤ_4-codes of lengths 56 and 64.
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