List questions from extremal-combinatorics

Published on 12 Apr 2026 - 9:36

103

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

Published on 16 Apr 2026 - 1:03

198

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Which integer partitions correspond to the most set partitions?

Published on 11 Apr 2026 - 13:08

321

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

Published on 16 Apr 2026 - 1:38

63

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Assignment of subsets with overlap rule

Published on 09 Apr 2026 - 23:37

216

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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 25 Mar 2026 - 12:51

28

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

Published on 16 Apr 2026 - 14:00

212

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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 14 Apr 2026 - 3:55

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

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

Published on 10 May 2026 - 16:11

116

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

Published on 10 May 2026 - 17:21

210

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References for combinatorics of finite sets

Published on 09 Apr 2026 - 12:24

66

Views

A doubt in the proof of Combinatorial nullstellensatz

Published on 10 May 2026 - 18:03

117

Views

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

Published on 10 May 2026 - 16:05

121

Views

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

Published on 10 May 2026 - 15:02

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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