User Andreas Caranti - Mathematics Stack Exchange

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	15,725 reputation	bio	website		visits	member for	4 months
1937 badges		location	Trento, Italy		seen	1 min ago

19

62

votes

6

answers

2

kviews

Find a real function, $f$, s.t. $f(f(x)) = -x$.

feb 25 at 19:56 Jacob Mayle 656

12

45

votes

12

answers

3

kviews

Is it morally right and pedagogically right to google answers to homework?

homework soft-question

sep 4 at 14:15 Ismael 1

14

41

votes

6

answers

727

views

Second part of the factorial sum divisibility question

elementary-number-theory

mar 27 at 17:27 Gottfried Helms 7,292

7

37

votes

2

answers

985

views

Do the Möbius function, totient function, sum of divisors and number of divisors uniquely specify a number?

number-theory

mar 27 at 11:48 azimut 5,588

18

36

votes

5

answers

1

kviews

Solutions to $\binom{n}{5} = 2 \binom{m}{5}$

probability combinatorics binomial-coefficients diophantine-equations

apr 19 at 2:27 Kundor 598

22

36

votes

7

answers

783

views

Problems regarding $\{x_n \}$ defined by $x_1=1$; $x_n$ is the smallest distinct natural number such that $x_1+…+x_n$ is divisible by $n$.

combinatorics sequences-and-series elementary-number-theory

mar 14 at 8:34 Marc van Leeuwen 24k

7

33

votes

2

answers

681

views

Do all natural numbers have a nonzero multiple that is a palindrome in base 10?

number-theory recreational-mathematics

may 19 at 8:42 P.. 8,945

9

33

votes

1

answer

1

kviews

Is Lagrange's theorem the most basic result in finite group theory?

abstract-algebra group-theory teaching proof-strategy

may 10 '11 at 20:41 joriki 92.8k

7

29

votes

3

answers

837

views

If $e^A$ and $e^B$ commute, do $A$ and $B$ commute?

linear-algebra exponential-function

apr 3 at 21:46 Seirios 8,977

12

28

votes

0

answers

1

kviews

Does a four-variable analog of the Hall-Witt identity exist?

abstract-algebra group-theory algebraic-topology intuition free-groups

jan 5 at 7:42 Alexander Gruber♦ 15.3k

6

26

votes

2

answers

473

views

Why is $\varphi$ called “the most irrational number”?

number-theory irrational-numbers golden-ratio

may 21 at 22:44 Oscar Cunningham 914

20

24

votes

3

answers

404

views

Square matrices satisfying certain relations must have dimension divisible by $3$

linear-algebra matrices contest-math

feb 26 at 10:26 YACP 9,245

12

23

votes

0

answers

847

views

$4494410$ and friends

algebra-precalculus elementary-number-theory arithmetic recreational-mathematics

may 10 at 23:04 Community♦ 1

7

21

votes

6

answers

536

views

Is $\mathbf{C}$ the algebraic closure of any field other than $\mathbf{R}$?

abstract-algebra field-theory

mar 3 at 18:00 JSchlather 9,750

8

21

votes

2

answers

220

views

Can commuting matrices $X,Y$ always be written as polynomials of some matrix $A$?

linear-algebra abstract-algebra matrices

mar 17 at 17:17 Marc van Leeuwen 24k

2

20

votes

2

answers

283

views

About translating subsets of $\Bbb R^2.$

geometry group-theory set-theory

feb 22 at 10:30 Tara B 4,098

4

16

votes

7

answers

1

kviews

Pythagorean triplets $x^2+y^2 = z^3$

number-theory diophantine-equations

may 22 at 6:41 Inceptio 4,910

2

15

votes

1

answer

375

views

Modules with $m \otimes n = n \otimes m$

commutative-algebra modules tensor-products

feb 15 at 7:48 Jonas Meyer 35.1k

7

14

votes

2

answers

217

views

Construct an example of set $A$ for which $A+A=A $ but $0∉cl(A)$

convex-analysis examples-counterexamples

feb 17 at 3:11 Community♦ 1

5

14

votes

1

answer

197

views

Galois group for $x^6-7x^2+7$

abstract-algebra

mar 18 at 22:16 Steve D 5,270

6

14

votes

1

answer

176

views

Fibonacci Sequence in $\mathbb Z_n$.

sequences-and-series group-theory fibonacci-numbers cyclic-groups

mar 13 at 1:50 Will Jagy 21.6k

4

14

votes

3

answers

328

views

An Elementary Number theory Problem

elementary-number-theory prime-numbers

may 13 at 9:29 Ivan Loh 7,603

4

13

votes

1

answer

110

views

The equivalence classes of $N\sim M\Leftrightarrow G/N\cong G/M$.

abstract-algebra group-theory finite-groups p-groups computational-algebra

mar 13 at 11:46 Andreas Caranti 15.7k

4

13

votes

2

answers

371

views

Formula for number of solutions to $x^4+y^4=1$, from Ireland and Rosen #8.18.

number-theory elementary-number-theory algebraic-number-theory finite-fields characters

feb 21 at 9:03 mercio 11.4k

8

12

votes

4

answers

248

views

Irreducibility of Polynomials in $k[x,y]$

algebraic-geometry commutative-algebra

feb 14 at 17:19 Hurkyl 21.6k

4

12

votes

2

answers

515

views

Daniel A. Marcus Number Fields Exercise 2.29

homework algebraic-number-theory

feb 23 at 1:30 Bruno 7,144

9

12

votes

1

answer

161

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$[(x-a_1)(x-a_2) \cdots (x-a_n)]^2 +1$ is irreducible over $\mathbb Q$

polynomials irreducible-polynomials

mar 1 at 11:24 YACP 9,245

6

12

votes

4

answers

1

kviews

If $a | m$ and $(a + 1) | m$, prove $a(a + 1) | m$.

number-theory

jan 25 at 0:45 Austin Mohr 11.7k

3

12

votes

2

answers

785

views

necessary and sufficient condition for trivial kernel of a matrix over a commutative ring

linear-algebra abstract-algebra matrices ring-theory

mar 10 at 22:50 joriki 92.8k

3

12

votes

3

answers

163

views

What is the order of $2$ in $(\mathbb{Z}/n\mathbb{Z})^\times$?

group-theory elementary-number-theory finite-groups

mar 13 at 20:02 zero-divisor 215

Andreas Caranti

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