List questions from combinatorial-proofs

Published on 14 Apr 2026 - 7:05

610

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A combinatorial proof of Euler's Criterion? $(\tfrac{a}{p})\equiv a^{\frac{p-1}{2}} \text{ mod p}$

Published on 10 May 2026 - 23:31

836

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Help with combinatorial proof of identity: $\sum_{k=1}^{n} \frac{(-1)^{k+1}}{k} \binom{n}{k} = \sum_{k=1}^{n} \frac{1}{k}$

Published on 13 Apr 2026 - 5:33

282

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Combinatorial proof involving reciprocals

Published on 10 Apr 2026 - 4:10

187

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How to Devise Combinatorial Arguments for Proving Identities

Published on 09 Apr 2026 - 2:35

203

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Prove this combinatorial identity

Published on 13 Apr 2026 - 13:24

150

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Combinatorial argument $a(n-a)$ $n \choose a $ = $n(n-1)$ $n-2 \choose a-1$

Published on 16 Apr 2026 - 22:35

338

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A sum with binomial coefficients in the numerator and denominator.

Published on 12 Apr 2026 - 5:19

617

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Help finding a combinatorial proof of $k {n \choose k } = n {n - 1 \choose k -1}\;$

Published on 12 Apr 2026 - 8:06

121

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Prove with combinatorial arguments this equation

Published on 17 Apr 2026 - 6:19

311

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Calculating $\sum_{k=1}^nk(k!)$ combinatorially

Published on 15 Apr 2026 - 16:31

405

Views

Proving that $\sum_{i = 0}^{m}{\binom{k+i}{k} \binom{n-i}{n-m}} = \binom{n+k+1}{m}$

Published on 17 Apr 2026 - 2:49

90

Views

Proving $\sum_{k=0}^n \binom{n}{k} = 2^n$ combinatorially?

Published on 14 Apr 2026 - 22:03

2.8k

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Combinatorial argument for the sum of the first $n$ integers.

Published on 15 Apr 2026 - 5:19

219

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Understanding a combinatorial relation.

Published on 10 Apr 2026 - 10:29

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Combinatorial proof of $n! = {n\choose k}k!(n-k)!$

A combinatorial proof of Euler's Criterion? $(\tfrac{a}{p})\equiv a^{\frac{p-1}{2}} \text{ mod p}$

Help with combinatorial proof of identity: $\sum_{k=1}^{n} \frac{(-1)^{k+1}}{k} \binom{n}{k} = \sum_{k=1}^{n} \frac{1}{k}$

Combinatorial proof involving reciprocals

How to Devise Combinatorial Arguments for Proving Identities

Prove this combinatorial identity

Combinatorial argument $a(n-a)$ $n \choose a $ = $n(n-1)$ $n-2 \choose a-1$

A sum with binomial coefficients in the numerator and denominator.

Help finding a combinatorial proof of $k {n \choose k } = n {n - 1 \choose k -1}\;$

Prove with combinatorial arguments this equation

Calculating $\sum_{k=1}^nk(k!)$ combinatorially

Proving that $\sum_{i = 0}^{m}{\binom{k+i}{k} \binom{n-i}{n-m}} = \binom{n+k+1}{m}$

Proving $\sum_{k=0}^n \binom{n}{k} = 2^n$ combinatorially?

Combinatorial argument for the sum of the first $n$ integers.

Understanding a combinatorial relation.

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