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COMBINATORICS
1998
14 years 10 months ago
1998
The permanent-determinant method and its generalization, the HafnianPfaffian method, are methods to enumerate perfect matchings of plane graphs that were discovered by P. W. Kaste...
COMBINATORICS
1998
14 years 10 months ago
1998
It is shown that there are 2n n − n−1 m=0 2n−m−1 2m m permutations which are the union of an increasing sequence and a decreasing sequence. 1991 Mathematics Subject Classi...
COMBINATORICS
1998
14 years 10 months ago
1998
Based on a recent improvement of the inclusion-exclusion principle, we present a new approach to network reliability problems. In particular, we give a new proof of a result of Sh...
COMBINATORICS
1998
14 years 10 months ago
1998
New lower bounds for 15 classical Ramsey numbers are established. Several of the colorings are found using a new variation of local search heuristics. Several others are found usi...
COMBINATORICS
1998
14 years 10 months ago
1998
We prove that the minimal length of a word Sn having the property that it contains exactly Fm+2 distinct subwords of length m for 1 ≤ m ≤ n is Fn + Fn+2. Here Fn is the nth Fi...