Gregarious GDDs with Two Associate Classes |
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Authors: | Saad I El-Zanati Narong Punnim Chris A Rodger |
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Institution: | 1. 4520 Mathematics Department, Illinois State University, Normal, IL, 61790-4520, USA 2. Department of Mathematics, Srinakharinwirot University, Sukhumvit 23, Bangkok, 10110, Thailand 3. Department of Mathematics and Statistics, Auburn University, 221 Parker Hall, Auburn, AL, 36849-5310, USA
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Abstract: | The existence of group divisible designs with two associate classes has been studied for over 50 years. Probably the most
difficult cases to solve are those in which the number of groups is less than the size of the blocks. Recently, such an existence
problem was solved in the case where the groups have the same size and the blocks have size 3. In this paper, we continue
to focus on blocks of size 3, solving the existence problem when the required designs are gregarious (each block intersects
each group). These designs are tight to construct in the sense that they satisfy equality in one of the bounds required for
GDDs to exist. |
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Keywords: | |
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