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120
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COMBINATORICS
2006
15 years 3 months ago
2006
A permutation is said to avoid the permutation if no subsequence in has the same order relations as . Two sets of permutations 1 and 2 are Wilfequivalent if, for all n, the numb...
122
Voted
COMBINATORICS
2006
15 years 3 months ago
2006
The rules of "Bulgarian solitaire" are considered as an operation on the set of partitions to induce a finite dynamical system. We focus on partitions with no preimage u...
115
Voted
COMBINATORICS
2006
15 years 3 months ago
2006
Let Sn be the group of permutations of [n] = {1, . . . , n}. The Bruhat order on Sn is a partial order relation, for which there are several equivalent definitions. Three well-kno...
114
Voted
COMBINATORICS
2006
15 years 3 months ago
2006
The group PGL(2, q), q = pn, p an odd prime, is 3-transitive on the projective line and therefore it can be used to construct 3-designs. In this paper, we determine the sizes of o...
108
Voted
COMBINATORICS
2006
15 years 3 months ago
2006
We investigate the existence of edge-magic labellings of countably infinite graphs by abelian groups. We show for that for a large class of abelian groups, including the integers ...