All Questions
Tagged with covering nt.number-theory
5 questions
21
votes
1
answer
771
views
Covering a set with geometric progressions
Consider the set $S_n=\{1,2,\cdots ,n\}$. What is the minimum number of distinct geometric progressions that cover $S_n$? Let us call this number $a_n$. I was wondering about this number after doing a ...
- 1,090
12
votes
1
answer
833
views
Are there infinitely many natural numbers not covered by one of these 7 polynomials?
Consider the following polynomials:
$$
f_1(n_1, m_1) = 30n_1m_1 + 23n_1 + 7m_1 + 5\\
f_2(n_2, m_2) = 30n_2m_2 + 17n_2 + 13m_2 + 7\\
f_3(n_3, m_3) = 30n_3m_3 + 23n_3 + 11m_3 + 8\\
f_4(n_4, m_4) = ...
- 123
5
votes
2
answers
388
views
How much do these interval collections cover?
As usual any related references are appreciated.
Let $p \lt q$ be distinct primes, and for all such pairs, let $m=pq$ and let $\cal{C}$ be the collection $(m-p,m)$ of open intervals. Does (the union ...
- 13k
1
vote
1
answer
378
views
Covering a finite subset of $\mathbb{N}$ with prime arithmetic progressions
Because of a problem I ran into I am trying to get a quick start in covering with arithmetic progressions.
First I want to say I am aware of this previously asked question:
Covering $\mathbb{N}$ with ...
- 11
0
votes
0
answers
120
views
Odd covering system without modulus 3 (mod3)
The existence of odd covering system with distinct moduli is a famous open question proposed by Erdős and Selfridge.
I wonder whether a restricted condition for the problem that odd covering system ...
- 101