List questions from examples-counterexamples

Published on 14 Apr 2026 - 11:52

333

Views

Legendre polynomials and primality testing

Published on 10 May 2026 - 11:18

134

Views

If $x \in \overline{A}$ implies $x$ is the limit of a sequence in $A$ for all $A \subset X$, is $X$ first-countable?

Published on 16 Apr 2026 - 0:32

65

Views

is there a harmonic function such that ${\partial f \over \partial r}$ isn't harmonic?

Published on 10 May 2026 - 15:50

98

Views

When do integrals converge, but absolute values of integrals not converge?

Published on 12 Apr 2026 - 5:30

62

Views

Example of curve in $R^2$ which kills driver affirmation

Published on 10 May 2026 - 15:51

375

Views

A congruence involving Fibonacci polynomials

Published on 10 May 2026 - 11:19

46

Views

$ A \subset \Bbb R$ is bounded and not compact, exhibit $f: A \to \Bbb R$ that isn't bounded

Published on 16 Apr 2026 - 3:27

165

Views

Elementary examples of pointwise sequential closures that are not pointwise closed

Published on 16 Apr 2026 - 12:47

537

Views

Counter-example for the Slutsky Theorem

Published on 14 Apr 2026 - 0:53

58

Views

Proofs by counter example

Published on 10 May 2026 - 21:14

49

Views

Does there exist a natural number $N = xy$ satisfying $D(x)D(y) = 2s(x)s(y)$ with $\gcd(x,y)=1$?

Published on 10 May 2026 - 13:51

49

Views

Does there exist an odd natural number $N = xy$ satisfying $D(x)D(y) = 2s(x)s(y)$?

Published on 10 May 2026 - 14:07

232

Views

Replacing Predicates in First Order Statements to Produce a Counter-Example World

Published on 14 Apr 2026 - 6:54

157

Views

A counterexample to the Sura-Bura Theorem for non separated compact spaces

Published on 11 May 2026 - 3:06

List Question

Example of normal subgroup that contains the commutator group as a proper subgroup.

Legendre polynomials and primality testing

If $x \in \overline{A}$ implies $x$ is the limit of a sequence in $A$ for all $A \subset X$, is $X$ first-countable?

is there a harmonic function such that ${\partial f \over \partial r}$ isn't harmonic?

When do integrals converge, but absolute values of integrals not converge?

Example of curve in $R^2$ which kills driver affirmation

A congruence involving Fibonacci polynomials

$ A \subset \Bbb R$ is bounded and not compact, exhibit $f: A \to \Bbb R$ that isn't bounded

Elementary examples of pointwise sequential closures that are not pointwise closed

Counter-example for the Slutsky Theorem

Proofs by counter example

Does there exist a natural number $N = xy$ satisfying $D(x)D(y) = 2s(x)s(y)$ with $\gcd(x,y)=1$?

Does there exist an odd natural number $N = xy$ satisfying $D(x)D(y) = 2s(x)s(y)$?

Replacing Predicates in First Order Statements to Produce a Counter-Example World

A counterexample to the Sura-Bura Theorem for non separated compact spaces

Trending Questions

Popular # Hahtags

Popular Questions