Questions on more advanced topics of number theory. Consider first if (elementary-number-theory) might be a more appropriate tag before adding this tag.

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0
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2answers
32 views

How prove this diophantine equation $x^2-y^2\equiv a\pmod p$ have only $p-1$roots

Question: let $a\neq 0$.and $p$ is prime numbers. show that the number of ordered two-tuples $(x,y)$such this following diophantine equation $$x^2-y^2\equiv a\pmod p$$ at most $p-1$ ...
16
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0answers
78 views

How many non-rational complex numbers $x$ have the property that $x^n$ and $(x+1)^n$ are rational?

In this answer, I proved the following statement: For each positive integer $n$, there are finitely many non-rational complex numbers $x$ such that $x^n$ and $(x+1)^n$ are rational. These complex ...
0
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0answers
24 views

What are some applications of parametrization of curves and surfaces?

I know that we can find all elements of a quadratic field with norm 1 by rational parametrization of conics, it can be used to show that some Diophantine equations are not so easy to solve, and that ...
2
votes
2answers
24 views

Classification of numbers on the base of binary representation

The problem is the following. I would like to find a simple algorithm or principle of classification of numbers regarding their presentation in binary form. Let's consider an example. The numbers by ...
6
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0answers
39 views

Source of Hardy-Littlewood's 2nd Conjecture

In what paper do Hardy and Littlewood first mention, specifically, their 2nd conjecture? It is not mentioned specifically in Partitio Numerorum III.
1
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2answers
56 views

About the infinitude of some kind of primes? [on hold]

I will propose this proof: A Mersenne number always has the form $$2^{p}-1=4n+3$$ since for all $p≥2$ we have $$2^{p}-1≡-1(mod4)≡3(mod4)$$ The Dirichlet prime number theorem ...
1
vote
1answer
18 views

Are Primitive Dirichlet Characters linearly independent.

For a positive integer $N$, let $$S_N=\{ \chi~\mid~ \chi \text{ is primitive Dirichlet characters modulo }F,\text{ where } F\mid N \}.$$ I want to check the Linear independence on $S_N$. More ...
6
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2answers
100 views

How to explain to a layman why Fermat's Last Theorem involves non-trivial math?

Fermat's Last Theorem states, given$$x^n + y^n = z^n$$ no three integers $x,y,z$ will satisfy the equation given integer value of $n$ greater than two. On the surface this seems like something that ...
0
votes
1answer
19 views

How to get the maximum and minimum number of length $m$ and the sum of the digits $s$

How to get the maximum and minimum of length $m$ and the sum of the digits $s$ By example: Length: 2 Sum of its digits: 15 Max: 96, Min: 69 Length: 2 Sum of its digits: 2 Max: 20, Min: 11
2
votes
1answer
29 views

Find $x$ such that $x \equiv7\pmod {37}$ and $x^2 \equiv 12\pmod {37^2}$

Find $x$ such that $x \equiv7 \pmod {37}$ and $x^2 \equiv 12\pmod {37^2})$ My attempt: Given $x \equiv7\pmod {37}$ so $37|(x-7)$ so $37^2|(x-7)^2$ so $x^2-14x+49 \equiv 0\pmod {37^2}$ as ...
6
votes
1answer
62 views

Number theory and abstract algebra question

So I was solving this question Find an isomorphism from the additive group $\mathbb Z_6$ to the multiplicative group of units $U_7$ in $\mathbb Z_7$. I found that $3$ is generator for U7 by brute ...
2
votes
3answers
49 views

Is there a number congruent to 1 modulo infinitely many primes?

Let $A=\left\{ p_{r},p_{r+1},\dots\right\}$ a (infinte) set of consecutive prime numbers (if you prefer, if $\mathfrak{P}$ is the set of all prime numbers, $A=\mathfrak{P}-\left\{ ...
0
votes
1answer
23 views

Hilbert class field whose class number is 1.

How to describe Hilbert class field of an imaginary quadratic field whose class number is 1 ? What happens to unramification at finite places ?
0
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1answer
23 views

Looking for methods for approximating an iterative equation regarding primes

In a previous question, I was looking for an equation for counting the number of the number of integers between $1$ and $x$ that have a prime factor besides $2$ or $3$. There were 2 iterative ...
1
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0answers
21 views

Decomposition of abelian varieties up to isogeny

Let $A_1,A_2,B_1,B_2$ be simple abelian varieties over a number field $k$. Suppose that $A_1\times A_2$ is $k$-isogenous to $B_1\times B_2$. Can we deduce that (up to reordering the factors) $A_1$ is ...
3
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1answer
79 views

Extending the zeta function to semiprimes, etc.

The Riemann Zeta function is defined for $s > 1$ as \begin{align} &\prod _{n=1}^{\infty}\dfrac{1}{1 -\ p_{n}^{\ \ -s}}\\ \end{align} It is possible to extend the zeta function to semiprimes ...
0
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1answer
40 views

Proving $m$ is prime when $a^{m-1}\equiv 1\pmod m$ and factors of $m-1$ satisy $a^n\equiv r\pmod m,r\neq1$

If $a^{m-1}\equiv 1\pmod m$, and all factors of $m-1$, say $n (n< m-1)$ satisfy $$a^n\equiv r\pmod m,r\neq1$$ then $m$ is a prime. I want to prove this proposition, but it is a little difficult ...
0
votes
1answer
19 views

Factorization with a Primitive Factor of Polynomials

Question: Let $f,g\in\Bbb Q[x]$. Why is it that $\rm\color{#c00}{(1)}$ if $f$ is monic then $f=\frac{1}{a}f^*$ for some primitive polynomial $f^*\in\Bbb Z[x]$ and $a\in\Bbb Z$ ? ...
4
votes
1answer
77 views

The Island in the Miracle Sea. (Christmas edition)

To all of you who love math like me, I have this puzzling riddle that I hope you find interesting : On Christmas Eve just after midnight, Santa was riding his sleigh over the Miracle Sea when ...
49
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3answers
642 views

A real number $x$ such that $x^n$ and $(x+1)^n$ are rational is itself rational

Let $x$ be a real number and let $n$ be a positive integer. It is known that both $x^n$ and $(x+1)^n$ are rational. Prove that $x$ is rational. What I have tried: Denote $x^n=r$ and $(x+1)^n=s$ ...
3
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2answers
40 views

Eigenvalues of a unimodular matrix

Let $U$ be a unimodular matrix, i.e. $U \in \mathbb{Z}^{n \times n}$, and $\text{det}(U) = \pm 1$. Do the real (or complex for that matter) eigenvalues of $U$ admit a special structure? Edit: It is ...
2
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1answer
36 views

How many distinct values of floor(N/i) exists for i=1 to N.

Say we have a function $F(i)=\text{floor}(N/i)$. Then how many distinct values of $F(i)$ will exist for all $0 \leq i \leq N$ e.g. We have $N=25$ then. $F(1)=25$ $F(2)=12$ $F(3)=8$ $F(4)=6$ ...
7
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0answers
57 views

If $p\equiv 1,9 \pmod{20}$ is a prime number, then there exist $a,b\in\mathbb{Z}$ such that $p=a^{2}+5b^{2}$.

I have to prove that if $p\equiv 1,9 \pmod{20}$ is a prime number then there exist $a,b\in\mathbb{Z}$ such that $p=a^{2}+5b^{2}$. I consider the quadratic field $\mathbb{Q}(\sqrt{-5})$, with ring of ...
4
votes
0answers
33 views

Kloosterman sum and multiples of 16

A Kloosterman sum is defined as $$K(a,b;m)=\sum_{0\leq x \leq m-1}_{\gcd(x,m)=1} e^{2\pi \mathcal{i} (ax+bx^*)/m}$$ where $a,b,m \in \mathbb{N}$ and $x^*$ is the inverse of $x$ modulo $m$. How can ...
1
vote
0answers
21 views

GCD of Arguments of Kloosterman Sum

A Kloosterman sum is defined as $$K(a,b;m)=\sum_{0\leq x \leq m-1}_{\gcd(x,m)=1} e^{2\pi \mathcal{i} (ax+bx^*)/m}$$ where $a,b,m \in \mathbb{N}$ and $x^*$ is the inverse of $x$ modulo $m$. It ...
0
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0answers
21 views

Why does this circulating decimal become equal with a natural number? [duplicate]

When I change the circulating decimal into correspondent fraction, it makes a natural number. What is the reason the two numbers become equal?
8
votes
1answer
162 views

How to solve $y^2=3x^4+3x^2+1$ for integers.

If $x,y \in \mathbb Z$ , then find all the solutions of $$y^2=3x^4+3x^2+1$$ I was asked this question by my friend who said that he encountered this while solving another problem. I have ...
9
votes
1answer
68 views

How many positive integers of n digits chosen from the set {2,3,7,9} are divisible by 3?

I'm preparing myself for math competitions. And I am trying to solve this problem from the Romanian Mathematical Regional Contest “Traian Lalescu’', $2003$: Problem $\mathbf{7}$: How many positive ...
2
votes
0answers
20 views

$GL_2(\mathbb{Q}_p)$ and $GL_2(\mathbb{Z}_p)\cdot\mathbb{Q}_p^\times$

I am confused by a question, which is probably of school level. In some papers I have seen an induction from the group $GL_2(\mathbb{Z}_p)\cdot\mathbb{Q}_p^\times$ to the group $GL_2(\mathbb{Q}_p)$, ...
1
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1answer
25 views

Factoring $x^{3}-6\in \mathbb{F}_{p}[x]$ when $p\equiv 1$ mod $3$.

If $p\equiv 1$ mod $3$, I know that $x^{3}-6$ has any solution in $\mathbb{F}_{p}$ if and only if there exist $A,B\in\mathbb{Z}$ such that $p=A^{2}+3B^{2}$ and $9|B$ or $9|(2B+A)$ or $9|(2B-A)$ (This ...
0
votes
2answers
65 views

Prove that as $x\to\infty $, $\sum\limits_{p \leq x} \frac{1}{p \log \log p} \approx \log \log \log x$

Prove that as $x\to\infty$, $$\sum_{p \leq x} \frac{1}{p \log \log p} \approx \log \log \log x$$ Here sum is taken over primes.I tried to use the partial summation formula but could not ...
0
votes
2answers
40 views

Convergence of a certain series of Primes

This is a problem from Alan Baker's Comprehensive Course in Number Theory. We have to show that $\displaystyle \sum\limits_{p} \frac{1}{p (\log\log p)^{\delta}}$ converges for all $\delta >1$.Here ...
0
votes
1answer
43 views

Beautiful Problem about pairwisely non-similar n-gons.

Let n be an integer (n>2). Show that there exists an infinite number of pairwisely non-similar inscribed n-gons, lengths of all sides and diagonals and areas of each of which are integers. My ...
0
votes
3answers
58 views

Find the n-th number from the generating function

Is there any way to find the n-th number in the series, by knowing it's genereting function. For example, I found that the closed form solution for a generating ...
4
votes
1answer
71 views

Why this happen only with $4,8,12,…$

We will take some examples to illustrate my question: If we take a set of numbers, for example $1,2$, and $3$ $$1+2^4+3^4=98$$ $$1+2^8+3^4=338$$ $$1+2^8+3^8=6818$$ $$1+2^8+3^{12}=531698$$ We note ...
2
votes
4answers
180 views

How can I prove the last digit of $(2^{121985292}-1)$ is $5$

My friend asked me this question, but I don't know how to prove it. Can anyone help me about this. Thanks
2
votes
0answers
70 views

Fermat's Challenge

This is a question French mathematician Pierre de Fermat posed to the English mathematicians of his time. "Prove that x=5 and y=3 are the only positive integer values for which $x^2 +2=y^3$." I have ...
0
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0answers
20 views

Why is it so difficult to use geometric methods to construct weight one modular forms?

I am trying to understand why it is that geometric methods of constructing modular forms of weight one for $SL(2,\mathbb Z)$ fail. I have a relatively rudimentary understanding of it, but it would be ...
1
vote
2answers
47 views

Prime in $\mathbb{Z}[i]$

I'd need a help with an exercise. I am trying to show that $(1-i)$ is a prime (or principal equivalently) ideal in $\mathbb{Z}[i]$. For doing this, I have not worked on the norms yet so I can't use ...
1
vote
1answer
60 views

Given a, b How many solutions exists for x, such that: $a \bmod{x}=b $

Given $a, b$. How many solutions exists for $x$, such that: $$a \bmod{x}=b $$ By example: $a = 21$ and $b = 5$ $21 \bmod{8} = 21 \bmod{16} = 5$ Then $x$ has 2 solutions
2
votes
2answers
89 views

Summing of factorials to produce perfect cubes

I was playing around with factorials the other day, and I realized that $4!+5!$ is a perfect square. Perplexed by this result, I started looking for other pairs of factorials that produce a perfect ...
19
votes
2answers
856 views

Unusual pattern in the distribution of odd primes

I have recently noticed an unusual pattern in the distribution of odd primes. Each one of the following sets contains approximately half of all odd primes: $A_n=\{4k+1: 0\leq k\leq ...
-1
votes
1answer
24 views

If $p\equiv 2$ mod $3$, $x^{3}\equiv a$ mod $p$ has only one solution modulo $p$.

Let $p$ be an odd prime and $a\in \mathbb{Z}$ such that $p\nmid a$. I have to show that if $p\equiv 2$ mod $3$, then $x^{3}\equiv a$ mod $p$ has only one solution modulo $p$. Using the properties of ...
4
votes
2answers
90 views

Number of solutions of a simple equation

Problem How to count the number of distinct integer solutions $(x_1,x_2,\dots,x_n)$ of the equations like : $$|x_1| + |x_2| + \cdots + |x_n| = d $$ the count gives the number of coordinate points ...
1
vote
1answer
43 views

Divisiblity by prime

Find minimum positive integer pair $(x,y)$ such that $P$ divides $|C^x−D^y|$. Here $P$ is a prime number and $C$ and $D$ are constants which are provided to us. For example, if $P=7$,$C=1$,$D=5$, the ...
2
votes
0answers
30 views

A question about a system of congruent equations? Is there a unified proof by using ring theory?

In his book ``Topics in number theory, Volumes I and II''. William J. Leveque proved the following theorem(see page 34) Theorem A necessary and sufficient condition that the system of congruences ...
1
vote
2answers
57 views

How prove each $k$ there exits infinite set of numbers $n$, are divisible by $m$

Prove that for each $k$ there exsit infinite set of numbers $n$, such that all the numbers $$\binom{n}{k},\binom{n+1}{k},\cdots,\binom{n+k-1}{k}$$ are divisible by $m$. I think we must use Kummer's ...
0
votes
1answer
22 views

How to find $x$ in $\left\lfloor{\frac{x-2000}{4}}\right\rfloor+x\equiv0\pmod 7$

Find all integers $x$ such that $2000\leq x\leq2100$ and $$\left\lfloor{\frac{x-2000}{4}}\right\rfloor+x\equiv0\pmod 7$$ Please, I have no idea how to proceed... any help is really appreciated
2
votes
2answers
51 views

Finding the different numbers whose sum squares give a number which has same digits

I could find the following numbers $$1+2^2+3^2+4^2+5^2=55$$ $$1+4^2+7^2=66$$ $$2^2+3^2+5^2+7^2+11^2+13^2+17^2=666$$ Are there other numbers ?
1
vote
0answers
55 views

Finding conjugacy classes and normal subgroups of $D_8$, the dihedral group of order $16$ [duplicate]

What are the conjugacy classes for the dihedral group $D_8$ of order 16? What are its subgroups of order $4$, and which of them are normal subgroups? I know that $\{e\} ...