List questions from extremal-combinatorics

Published on 25 Mar 2026 - 7:39

100

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Lower bound for $\sum_{v \in V(G)} d(v)\bar{d}(v)$

Published on 04 Jun 2019 - 4:43

195

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Which integer partitions correspond to the most set partitions?

Published on 06 Jun 2019 - 20:57

318

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Ramsey number: why is R(s, t)=R(t, s)?

Published on 10 Jun 2019 - 7:15

61

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Assignment of subsets with overlap rule

Published on 13 Jun 2019 - 7:46

215

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The drawn diagonals divide the $N\times N$ board into $K$ regions. For each $N$, determine the smallest and the largest possible values of $K$.

Published on 22 Mar 2026 - 19:35

25

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Find a quasi-random subgraph of linear size in a given graph.

Published on 26 Jul 2019 - 8:52

210

Views

Prove that out of nine random people, there can always be found three people who know one another or four people who don't know one another.

Published on 04 Aug 2019 - 13:19

262

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Family of $r$-subsets, all pair-wise intersecting in $s$ elements

Published on 25 Mar 2026 - 4:40

2.2k

Views

Graph with $2n$ vertices and $n^2+1$ edges has at least $n$ triangles.

Published on 16 Mar 2026 - 17:40

113

Views

Minimal set of $n\times n$ matrices whose products generate all $n\times n$ matrices with a single $1$

Published on 25 Mar 2026 - 4:42

207

Views

References for combinatorics of finite sets

Published on 10 Aug 2019 - 9:40

65

Views

A doubt in the proof of Combinatorial nullstellensatz

Published on 25 Mar 2026 - 10:55

116

Views

Minimal lower triangular sum of a $5\times 5$ Latin square

Published on 25 Mar 2026 - 7:47

120

Views

Tighter lower bound of the lower triangular sum of an arbitrary Latin square

Published on 25 Mar 2026 - 9:31

List Question

How many vertices can a hypercube-hyperplane intersection have?

Lower bound for $\sum_{v \in V(G)} d(v)\bar{d}(v)$

Which integer partitions correspond to the most set partitions?

Ramsey number: why is R(s, t)=R(t, s)?

Assignment of subsets with overlap rule

The drawn diagonals divide the $N\times N$ board into $K$ regions. For each $N$, determine the smallest and the largest possible values of $K$.

Find a quasi-random subgraph of linear size in a given graph.

Prove that out of nine random people, there can always be found three people who know one another or four people who don't know one another.

Family of $r$-subsets, all pair-wise intersecting in $s$ elements

Graph with $2n$ vertices and $n^2+1$ edges has at least $n$ triangles.

Minimal set of $n\times n$ matrices whose products generate all $n\times n$ matrices with a single $1$

References for combinatorics of finite sets

A doubt in the proof of Combinatorial nullstellensatz

Minimal lower triangular sum of a $5\times 5$ Latin square

Tighter lower bound of the lower triangular sum of an arbitrary Latin square

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