Question

What is the largest known prime of the form $(3^n + 1)/4$?

score 149 · Answer 1 · 2026-04-06 03:13:12

149

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What is the largest known prime of the form $(3^n + 1)/4$?

Published on 06 Apr 2026 - 3:13

score 64 · Answer 2 · 2026-03-27 06:01:42

64

Views

Example for $[G : G\cap H] \neq [H:G\cap H]$ with isomorphic subgroups $G \cong H$?

Published on 27 Mar 2026 - 6:01

score 82 · Answer 3 · 2026-04-04 02:25:29

82

Views

Strict partial order and strict linear order

Published on 04 Apr 2026 - 2:25

score 108 · Answer 4 · 2026-04-05 09:04:51

108

Views

Let $0<\alpha\leq\frac{\pi^2}{6}.\ $ Does $\exists\ A\subset\mathbb{N}$ and $f:A\to\{-1,1\}$ such that $\sum_{n\in A} \frac{f(n)}{n^2}=\alpha?$

Published on 05 Apr 2026 - 9:04

score 33 · Answer 5 · 2026-02-23 23:49:55

33

Views

Counter example: continuity assumption of mean value theorem

Published on 23 Feb 2026 - 23:49

score 45 · Answer 6 · 2026-03-26 16:06:04

45

Views

"Explicit" showing of non-flatness for a fractional ideal

Published on 26 Mar 2026 - 16:06

score 51 · Answer 7 · 2026-03-25 07:49:24

51

Views

Counterexamples to $\hat{A} \otimes_A M \cong \hat{M}$

Published on 25 Mar 2026 - 7:49

score 77 · Answer 8 · 2026-02-23 07:24:19

77

Views

$m_i, n_j$ integers and $\{m_i\}_{i=1}^{k}\neq\{n_j\}_{j=1}^{k'}.$ Does $\sum\frac{1}{m_i}=\sum\frac{1}{n_j}\implies\sum m_i\neq\sum n_j?$

Published on 23 Feb 2026 - 7:24

score 105 · Answer 9 · 2026-03-25 07:49:27

105

Views

Example of two group filtrations that induce different topologies but the same completion

Published on 25 Mar 2026 - 7:49

score 47 · Answer 10 · 2024-01-31 04:13:59

47

Views

What are the compactness properties of $\mathbb R$, extended by a point with co-countable open neighborhoods?

Published on 31 Jan 2024 - 4:13

score 68 · Answer 11 · 2024-02-01 04:40:00

68

Views

How to find solutions of PDEs or explain they don't exist

Published on 01 Feb 2024 - 4:40

score 80 · Answer 12 · 2024-02-02 08:56:48

Is there a function $f : \mathbb{R}-\{ 0\} \to \mathbb{R}$ such that $f(x)= - f(2x)$ for all $x \in \mathbb{R}-\{ 0\}$ , $f(x) \ne 0$?

score 76 · Answer 13 · 2026-03-29 05:44:15

76

Views

Does $\exists\ n$ such that the first $2n$ digits of Thue Morse, $X_{2n},$ is the concatenated sequence $X_n X_n?$ If not then why not?

Published on 29 Mar 2026 - 5:44

score 500 · Answer 14 · 2024-02-03 17:01:58

500

Views

Looking for a counterexample for this statement regarding divergent series

Published on 03 Feb 2024 - 17:01

score 72 · Answer 15 · 2026-03-26 06:01:37

72

Views

Are there contiguous sequences of prime numbers of length $k$ which are convex (similarly, concave) for every $k\in\mathbb{N}?$

Published on 26 Mar 2026 - 6:01

List Question

What is the largest known prime of the form $(3^n + 1)/4$?

Example for $[G : G\cap H] \neq [H:G\cap H]$ with isomorphic subgroups $G \cong H$?

Strict partial order and strict linear order

Let $0<\alpha\leq\frac{\pi^2}{6}.\ $ Does $\exists\ A\subset\mathbb{N}$ and $f:A\to\{-1,1\}$ such that $\sum_{n\in A} \frac{f(n)}{n^2}=\alpha?$

Counter example: continuity assumption of mean value theorem

"Explicit" showing of non-flatness for a fractional ideal

Counterexamples to $\hat{A} \otimes_A M \cong \hat{M}$

$m_i, n_j$ integers and $\{m_i\}_{i=1}^{k}\neq\{n_j\}_{j=1}^{k'}.$ Does $\sum\frac{1}{m_i}=\sum\frac{1}{n_j}\implies\sum m_i\neq\sum n_j?$

Example of two group filtrations that induce different topologies but the same completion

What are the compactness properties of $\mathbb R$, extended by a point with co-countable open neighborhoods?

How to find solutions of PDEs or explain they don't exist

Is there a function $f : \mathbb{R}-\{ 0\} \to \mathbb{R}$ such that $f(x)= - f(2x)$ for all $x \in \mathbb{R}-\{ 0\}$ , $f(x) \ne 0$?

Does $\exists\ n$ such that the first $2n$ digits of Thue Morse, $X_{2n},$ is the concatenated sequence $X_n X_n?$ If not then why not?

Looking for a counterexample for this statement regarding divergent series

Are there contiguous sequences of prime numbers of length $k$ which are convex (similarly, concave) for every $k\in\mathbb{N}?$

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