#### Computational Results of Duadic Double Circulant Codes

##### Sunghyu Han, Jon-Lark Kim

Quadratic residue codes have been one of the most important classes of algebraic codes. They have been generalized into duadic codes and quadratic double circulant codes. In this paper we introduce a new subclass of double circulant codes, called {\em{duadic double circulant codes}}, which is a generalization of quadratic double circulant codes for prime lengths. This class generates optimal self-dual codes, optimal linear codes, and linear codes with the best known parameters in a systematic way. We describe a method to construct duadic double circulant codes using 4-cyclotomic cosets and give certain duadic double circulant codes over $\mathbb F_2, \mathbb F_3, \mathbb F_4, \mathbb F_5$, and $\mathbb F_7$. In particular, we find a new ternary self-dual $[76,38,18]$ code and easily rediscover optimal binary self-dual codes with parameters $[66,33,12]$, $[68,34,12]$, $[86,43,16]$, and $[88,44,16]$ as well as a formally self-dual binary $[82,41,14]$ code.

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