科研之友
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摘要
In this article, we first show that a group divisible 3-design with block sizes from 14, 6), index unity and group-type 2(m) exists for every integer m >= 4 with the exception of m = 5. Such group divisible 3-designs play an important role in our subsequent complete solution to the existence problem for directed H-designs DH(lambda)(m, r, 4, 3)s. We also consider a way to construct optimal codes capable of correcting one deletion or insertion using the directed H-designs. In this way, the optimal single-deletion/insertion-correcting codes of length 4 can be constructed for all even alphabet sizes.
