On arithmetic partitions of Z_n

Generalizing a classical problem in enumerative combinatorics, Mansour and Sun counted the number of subsets of $\Z_n$ without certain separations. Chen, Wang, and Zhang then studied the problem of partitioning $\Z_n$ into arithmetical progressions of a given type under some technical conditions. In this paper, we improve on their main theorems by applying a convolution formula for cyclic multinomial coefficients due to Raney-Mohanty.Comment: 10 pages, 1 figure, European J. Combin. (2008), doi:10.1016/j.ejc.2008.11.00

The number of s-separated k-sets in various circles

This article studies the number of ways of selecting k objects arranged in p circles of sizes n0,...,np−1 such that no two selected ones have less than s objects between them. If ni ≥ sk + 1 for all 0 ≤ i ≤ p − 1, this number is shown to be n0+...+np−2 k n0+...+np−2−sk−1 k−1 . A combinatorial proof of this claim is provided, and two convolution formulas due to Rothe are obtained as corollaries.Fil: Estrugo, Emiliano Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Pastine, Adrián Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentin