نتایج جستجو برای: permutation
تعداد نتایج: 15423 فیلتر نتایج به سال:
We determine all permutation classes defined by pattern avoidance which are equinumerous to the class of permutations whose Schubert variety is smooth. We also provide a lattice path interpretation for the numbers of such permutations.
The cyclic closure of a permutation pattern class is defined as the set of all the cyclic rotations of its permutations. Examples of finitely based classes whose cyclic closure is also finitely based are given, as well as an example where the cyclic closure is not finitely based. Some enumerations of cyclic closures are computed.
Ascent sequences are sequences of nonnegative integers with restrictions on the size of each letter, depending on the number of ascents preceding it in the sequence. Ascent sequences have recently been related to (2+2)-free posets and various other combinatorial structures. We study pattern avoidance in ascent sequences, giving several results for patterns of lengths up to 4, for Wilf equivalen...
the full automorphism group of $u_6(2)$ is a group of the form $u_6(2){:}s_3$. the group $u_6(2){:}s_3$ has a maximal subgroup $2^9{:}(l_3(4){:}s_3)$ of order 61931520. in the present paper, we determine the fischer-clifford matrices (which are not known yet) and hence compute the character table of the split extension $2^9{:}(l_3(4){:}s_3)$.
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