178 search results - page 18 / 36 » combinatorics 2007 |
107
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COMBINATORICS
2007
15 years 3 months ago
2007
Let Sn denote the symmetric group on [n] = {1, . . . , n}. A family I ⊆ Sn is intersecting if any two elements of I have at least one common entry. It is known that the only int...
106
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COMBINATORICS
2007
15 years 3 months ago
2007
By introducing the notion of relative derangements of type B, also called signed relative derangements, which are defined in terms of signed permutations, we obtain a type B anal...
COMBINATORICS
2007
15 years 3 months ago
2007
We define an excedance number for the multi-colored permutation group i.e. the wreath product (Zr1 × · · · × Zrk ) Sn and calculate its multi-distribution with some natural ...
109
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COMBINATORICS
2007
15 years 3 months ago
2007
Using a recent result of Chudnovsky, Seymour, and Sullivan, we slightly improve two bounds related to the Caccetta-Haggkvist Conjecture. Namely, we show that if α ≥ 0.35312, th...
104
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COMBINATORICS
2007
15 years 3 months ago
2007
We determine the exact and asymptotic number of unlabeled outerplanar graphs. The exact number gn of unlabeled outerplanar graphs on n vertices can be computed in polynomial time,...