User Jernej

9

36

votes

1

answer

4k

views

A generalisation of the equation $n = ab + ac + bc$

nt.number-theory

Dec 15 at 20:53 YCor 43.6k

9

27

votes

9

answers

5k

views

Is the empty graph a tree?

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3

19

votes

3

answers

1k

views

A generalization of the triangle counting problem for simple weighted graphs

co.combinatorics graph-theory algorithms computational-complexity enumerative-combinatorics

May 9 '16 at 20:03 Community♦ 1

1

18

votes

1

answer

712

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Showing that a certain matrix is not positive definite

linear-algebra matrices eigenvalues

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4

16

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2

answers

1k

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Minimal graphs with a prescribed number of spanning trees

graph-theory extremal-graph-theory co.combinatorics open-problems

Feb 18 '13 at 21:15 Community♦ 1

7

15

votes

5

answers

7k

views

Upper bounds for the sum of primes up to $n$

nt.number-theory analytic-number-theory prime-number-theorem

May 25 at 5:42 J. W. Tanner 171

13

votes

1

answer

750

views

Tutte polynomials, graph complements and degree sequences

graph-theory co.combinatorics algebraic-graph-theory tutte-polynomial

Jun 5 '13 at 10:54 joro 22.1k

9

12

votes

6

answers

8k

views

Frobenius number for three numbers

nt.number-theory reference-request

Nov 23 '19 at 15:38 smichr 101

3

11

votes

1

answer

341

views

A variant of Cholesky decomposition involving binary matrices

linear-algebra matrices matrix-theory matrix-equations

Jun 9 '14 at 10:38 Jernej 3,243

4

11

votes

1

answer

888

views

Is every matching of the hypercube graph extensible to a Hamiltonian cycle

co.combinatorics graph-theory open-problems

Sep 27 '13 at 8:46 Sergiy Kozerenko 737

1

8

votes

4

answers

1k

views

Prime numbers $p$ not of the form $ab + bc + ac$ $(0 < a < b < c )$ (and related questions)

graph-theory nt.number-theory analytic-number-theory prime-numbers

Nov 25 '15 at 19:31 Community♦ 1

1

8

votes

2

answers

225

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Isomorphism problem on the class of induced subgraphs of a hypercube

graph-theory algorithms computational-complexity isomorphism-testing

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8

votes

3

answers

393

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An inequality related to the number of binary strings with no fixed substring

co.combinatorics inequalities

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4

8

votes

1

answer

315

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Maximal class of simple graphs of order $n$ with mutually distinct numbers of spanning trees

graph-theory extremal-graph-theory co.combinatorics open-problems

Aug 4 '13 at 9:58 Community♦ 1

7

votes

1

answer

342

views

Induced subgraphs of small strongly regular graphs

co.combinatorics graph-theory

Jan 30 '15 at 9:48 Dima Pasechnik 12.3k

2

7

votes

1

answer

721

views

(The) missing Moore graph(s) - uniqueness

graph-theory algebraic-graph-theory co.combinatorics

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2

7

votes

3

answers

1k

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Randomly contracting edges of a graph - expected number of vertices?

pr.probability graph-theory

Jul 16 '11 at 9:05 Seva 20.2k

1

6

votes

5

answers

2k

views

The missing Euler Idoneal numbers

nt.number-theory reference-request algebraic-number-theory

Jun 5 '18 at 18:33 GH from MO 76.5k

1

6

votes

2

answers

735

views

Minimal graphs of prescribed girth and chromatic number

co.combinatorics graph-theory graph-colorings extremal-graph-theory

Jan 13 '15 at 8:59 Florent Foucaud 527

6

votes

1

answer

519

views

Probability that a random edge coloring of the complete graph is proper

co.combinatorics graph-theory graph-colorings

Aug 10 '13 at 7:24 Community♦ 1

4

5

votes

1

answer

241

views

A variant of Ramsey numbers

reference-request co.combinatorics graph-theory ramsey-theory

Sep 30 '16 at 9:08 David Conlon 681

5

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0

answers

292

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Graphs with many positive eigenvalues of their distance matrix

co.combinatorics graph-theory algebraic-graph-theory

Oct 1 '13 at 14:59 Jernej 3,243

4

5

votes

2

answers

693

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Neat results from algebraic graph theory

graph-theory algebraic-graph-theory big-list

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4

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1

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474

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Generating non-isomorphic graphs by adding edges to a given graph

co.combinatorics graph-theory algorithms

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4

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Determine if a graph has a large clique

co.combinatorics graph-theory soft-question algorithms

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2

4

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3

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228

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Almost all graphs have a subgraph from a large class of graphs with constant order

graph-theory extremal-graph-theory co.combinatorics

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2

answers

1k

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Upper bound for a+b+c in terms of ab+bc+ac

inequalities

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2

4

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2

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785

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Asymptotics for the number of ways to sum primes such that the sum is <= n

inequalities sequences-and-series prime-numbers nt.number-theory asymptotics

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2

4

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0

answers

396

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Number of $k$-partitions of $n$ into odd prime parts

nt.number-theory prime-numbers

Jul 9 '11 at 19:26 Jernej 3,243

4

votes

1

answer

253

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Connected graphs that are not 2 connected

asymptotics graph-theory

Mar 18 '11 at 13:19 Igor Rivin 92.2k

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45 Questions

A generalisation of the equation $n = ab + ac + bc$

Is the empty graph a tree?

A generalization of the triangle counting problem for simple weighted graphs

Showing that a certain matrix is not positive definite

Minimal graphs with a prescribed number of spanning trees

Upper bounds for the sum of primes up to $n$

Tutte polynomials, graph complements and degree sequences

Frobenius number for three numbers

A variant of Cholesky decomposition involving binary matrices

Is every matching of the hypercube graph extensible to a Hamiltonian cycle

Prime numbers $p$ not of the form $ab + bc + ac$ $(0 < a < b < c )$ (and related questions)

Isomorphism problem on the class of induced subgraphs of a hypercube

An inequality related to the number of binary strings with no fixed substring

Maximal class of simple graphs of order $n$ with mutually distinct numbers of spanning trees

Induced subgraphs of small strongly regular graphs

(The) missing Moore graph(s) - uniqueness

Randomly contracting edges of a graph - expected number of vertices?

The missing Euler Idoneal numbers

Minimal graphs of prescribed girth and chromatic number

Probability that a random edge coloring of the complete graph is proper

A variant of Ramsey numbers

Graphs with many positive eigenvalues of their distance matrix

Neat results from algebraic graph theory

Generating non-isomorphic graphs by adding edges to a given graph

Determine if a graph has a large clique

Almost all graphs have a subgraph from a large class of graphs with constant order

Upper bound for a+b+c in terms of ab+bc+ac

Asymptotics for the number of ways to sum primes such that the sum is <= n

Number of $k$-partitions of $n$ into odd prime parts

Connected graphs that are not 2 connected