User Jeppe Stig Nielsen

28 votes

2 answers

659 views

A number $n$ which is the sum of all numbers $k$ with $\sigma(k)=n$?

asked Jan 30, 2015 at 20:41

25 votes

1 answer

593 views

Integers $n$ for which the digit sum of $n$ exceeds the digit sum of $n^5$

asked Aug 18, 2015 at 18:58

13 votes

1 answer

330 views

Locus of points such that facing Mecca is the same as facing east

asked Jan 6, 2017 at 18:22

11 votes

0 answers

316 views

If $b$ is even and not a power of two, can $b^4+1$ be a Fermat pseudoprime base 2?

asked Mar 7, 2016 at 22:28

10 votes

1 answer

256 views

When does the $f^{(n)}$ converge to a limit function as $n\to\infty$?

asked Aug 30, 2017 at 19:43

10 votes

1 answer

345 views

Can a composite number $3\cdot 2^n + 1$ divide a Fermat number $2^{2^m}+1$?

asked Apr 24, 2020 at 15:50

8 votes

2 answers

180 views

Probability of each type of inscribed octahedron

asked Mar 14 at 16:57

7 votes

1 answer

482 views

Classify groups all of whose subgroups are nested

asked Oct 18, 2016 at 12:49

6 votes

1 answer

358 views

Could a Mersenne prime divide an odd perfect number?

asked May 27, 2018 at 20:34

5 votes

0 answers

219 views

Is there a known method for finding extremely huge squarefree numbers?

asked Apr 19, 2014 at 22:59

4 votes

0 answers

145 views

For cardinals, if $\mathfrak{a}\ne\mathfrak{b}$ then $2^\mathfrak{a}\ne 2^\mathfrak{b}$

asked Nov 21, 2014 at 16:19

4 votes

2 answers

411 views

Criterion for sum/difference of unit fractions to be in lowest terms

asked Jun 16, 2013 at 13:44

3 votes

2 answers

822 views

Does every normal number have irrationality measure $2$?

asked Dec 22, 2013 at 23:16

2 votes

1 answer

92 views

Simple inequality with products of finite geometric series

asked Oct 15, 2018 at 18:59

1 vote

0 answers

47 views

Repeatedly multiplying by numbers taken from a uniform distribution

asked Dec 8, 2018 at 10:34

1 vote

1 answer

63 views

Is the multiplicative order of $n$ modulo a Cullen prime always a power of two?

asked Aug 16, 2023 at 6:18

0 votes

1 answer

118 views

What are some ("small") Riesel numbers without a covering set?

asked Jul 22, 2020 at 22:54

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17 Questions

A number $n$ which is the sum of all numbers $k$ with $\sigma(k)=n$?

Integers $n$ for which the digit sum of $n$ exceeds the digit sum of $n^5$

Locus of points such that facing Mecca is the same as facing east

If $b$ is even and not a power of two, can $b^4+1$ be a Fermat pseudoprime base 2?

When does the $f^{(n)}$ converge to a limit function as $n\to\infty$?

Can a composite number $3\cdot 2^n + 1$ divide a Fermat number $2^{2^m}+1$?

Probability of each type of inscribed octahedron

Classify groups all of whose subgroups are nested

Could a Mersenne prime divide an odd perfect number?

Is there a known method for finding extremely huge squarefree numbers?

For cardinals, if $\mathfrak{a}\ne\mathfrak{b}$ then $2^\mathfrak{a}\ne 2^\mathfrak{b}$

Criterion for sum/difference of unit fractions to be in lowest terms

Does every normal number have irrationality measure $2$?

Simple inequality with products of finite geometric series

Repeatedly multiplying by numbers taken from a uniform distribution

Is the multiplicative order of $n$ modulo a Cullen prime always a power of two?

What are some ("small") Riesel numbers without a covering set?