Izaak van Dongen's user avatar
Izaak van Dongen's user avatar
Izaak van Dongen's user avatar
Izaak van Dongen
  • Member for 6 years, 6 months
  • Last seen this week
18 votes
Accepted

The set of all groups

13 votes

A formula for any finite sequence of number

10 votes

Determining the minor radius of an ellipse from its major axis and a tangent line

9 votes
Accepted

On the isomorphism $\mathbb{R} \cong \mathbb{R}^2$

6 votes
Accepted

Different Hausdorff topologies with the same continuous mappings

6 votes
Accepted

Is $\mathrm{Z}$ an elementary submodel of $\mathrm{Z} [x_1, x_2, \dots]$?

5 votes

Can $⟨a_n⟩$ be oscillatory if $\lim_{n\rightarrow\infty}a_{n+1}/a_n = 1$?

5 votes
Accepted

Logarithm Subtraction and Division with Same Bases

5 votes
Accepted

Proof by induction using summation

5 votes
Accepted

Is every group isomorphic to a set of isomorphisms?

5 votes
Accepted

Is a finite semigroup with a unique idempotent $e$ always a group with unit $e$?

4 votes
Accepted

Function that is constant on connected components but not locally constant

4 votes

On the product of two finitely generated $\Omega$-algebras.

4 votes
Accepted

Sufficient condition for multiplication to be continuous

4 votes
Accepted

Counting (0,1)-matrices with a given characteristic polynomial

4 votes
Accepted

Is some convex combination of vectors in the same direction as all those vectors?

4 votes
Accepted

All terms of the sequence are "$x^2+(x+1)^2$"

3 votes

If $f$ is not bounded from above, then $\lim_{x \to b^{-}}f(x) = \infty$ - Feedback on attempted proofs

3 votes
Accepted

Connected components of real matrices such that $M^2=I$

3 votes

Matrix times eigenspace associated to its eigenvalue

3 votes
Accepted

A structure around $n \equiv p^k \pmod q$?

3 votes

Trigonometry: Tan Numerator Divide by Tan Denom

3 votes

What does "relation induced by a partition" mean?

3 votes
Accepted

Expectation of the absolute value of $X$ if $E[X]=0$

3 votes
Accepted

Find the smallest real number $M$ for which $\{a\} + \{b\} + \{c\} ≤ M$

3 votes
Accepted

Hereditary and transitive set that is not a stage

3 votes
Accepted

Is every regular Alexandrov topology a partition topology?

3 votes

What is the set generate by ${1}$ and a function $1/(a+b)$?

2 votes
Accepted

Why are the $n$th-order differences of the sequences $a^n$ always equal to $n!$?

2 votes
Accepted

Number of compositions of $2n$ with the largest part exactly $n$