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For questions related to teaching mathematics. For questions in Mathematics Education as a scientific discipline there is also the tag mathematics-education. Note you may also ask your question on http://matheducators.stackexchange.com/.

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The Matrix-Tree Theorem without the matrix

A combinatorial proof of the matrix-tree theorem can be found in the paper by D. Zeilberger A combinatorial approach to matrix algebra, Discrete Math. 56 (1985), 61–72. The proof uses only the interp …
Ira Gessel's user avatar
7 votes

Seeking a combinatorial proof for a binomial identity

Here are some observations, though not quite a combinatorial proof of the identity in question. Let $A(m,n)$ be the value of the sums. Let $B(m,n)=(-1)^m A(m, m+n)$. Then $B(m,n)$ is nonnegative for a …
Ira Gessel's user avatar