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Tag Archives: Dima Fon-Der-Flaass
Bijective proofs
A fourth proof Last month I described three proofs of the formula for the number of ways to choose k objects from a set of n, if repetition is allowed and order is not significant; it is the same as … Continue reading
Posted in exposition, open problems
Tagged bijections, Catalan numbers, Catalan objects, Dima Fon-Der-Flaass, permutations, sampling
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The definition of a matroid
This post continues my series about definitions. It has been obvious from the earliest days of the subject that matroids can be defined in very many different ways: in terms of their independent sets, their bases (maximal independent sets), their … Continue reading
Posted in exposition
Tagged 1-skeleton, cryptomorphic, Dima Fon-Der-Flaass, exchange axiom, IBIS family, optimization, polytope, Takeo Nakasawa
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