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COMBINATORICS
1998
88views more  COMBINATORICS 1998»
13 years 6 months ago
Multi-statistic enumeration of two-stack sortable permutations
Using Zeilberger’s factorization of two-stack-sortable permutations, we write a functional equation — of a strange sort — that defines their generating function according t...
Mireille Bousquet-Mélou
COMBINATORICS
1998
60views more  COMBINATORICS 1998»
13 years 6 months ago
Finite Vector Spaces and Certain Lattices
The Galois number Gn(q) is defined to be the number of subspaces of the n-dimensional vector space over the finite field GF(q). When q is prime, we prove that Gn(q) is equal to...
Thomas W. Cusick
COMBINATORICS
1998
130views more  COMBINATORICS 1998»
13 years 6 months ago
Codes and Projective Multisets
The paper gives a matrix-free presentation of the correspondence between full-length linear codes and projective multisets. It generalizes the BrouwerVan Eupen construction that t...
Stefan M. Dodunekov, Juriaan Simonis
COMBINATORICS
1998
91views more  COMBINATORICS 1998»
13 years 6 months ago
New Bounds for Union-free Families of Sets
: Following Frankl and F¨uredi [1] we say a family, F, of subsets of an n-set is weakly union-free if F does not contain four distinct sets A, B, C, D with A ∪ B = C ∪ D. If i...
Don Coppersmith, James B. Shearer
COMBINATORICS
1998
103views more  COMBINATORICS 1998»
13 years 6 months ago
Recognizing Circulant Graphs of Prime Order in Polynomial Time
A circulant graph G of order n is a Cayley graph over the cyclic group Zn. Equivalently, G is circulant iff its vertices can be ordered such that the corresponding adjacency matr...
Mikhail E. Muzychuk, Gottfried Tinhofer