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COMBINATORICS
2004
14 years 9 months ago
2004
We present a class of permutations for which the number of distinctly ordered subsequences of each permutation approaches an almost optimal value as the length of the permutation ...
COMBINATORICS
2004
14 years 9 months ago
2004
Let (a1, a2,
COMBINATORICS
2004
14 years 9 months ago
2004
We give the construction of a free commutative unital associative Nijenhuis algebra on a commutative unital associative algebra based on an augmented modified quasi-shuffle produc...
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COMBINATORICS
2004
14 years 9 months ago
2004
Given a sequence {Qn(x)} n=0 of symmetric orthogonal polynomials, defined by a recurrence formula Qn(x) = n
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COMBINATORICS
2004
14 years 9 months ago
2004
An antichain is a collection of sets in which no two sets are comparable under set inclusion. An antichain A is flat if there exists an integer k 0 such that every