Tagged Questions

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$2p-2$ as the sum of consecutive prime numbers

Progress: Let $p$ be a prime such that $p≡1$ (mod 6) then $2p-2$ can be written uniquely (up to the order of addends) as the sum of some consecutive prime numbers. These are first ten examples: ...
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$n^2-79n+1601$ always a prime?

I am struggling with proving or disproving this: $n^2-79n+1601$ is a prime for all natural numbers $n$ (except multiples of $1601$). This somehow has a relation to Stanislaw Ulam spiral. What ...
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Induction hypothesis misunderstanding and the fundamental theorem of arithmetic.

The fundamental theorem of arithmetic is made of two parts: The existence part: There exist primes such that for any natural number $j$, we can write $j$ as a product of prime numbers. The ...
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Questions about central polygonal numbers $1, 2, 4, 7, 11, 16, 22, 29, 37, 46,\cdots$

Formula for Central polygonal numbers is $\frac{n(n+1)}{2} + 1$, if $n=1$ or $n$ is prime, we get the new sequence $A$: 2, 4, 7, 16, 29, 67, 92, 154, 191, ... It seems that all primes either is ...
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Can a Mersenne number be a power (with exponent > 1) of a prime?

Let $n \geq 1$ and consider the (Mersenne) number $M_n = 2^n-1$. Is it possible that $M_n = p^k$ for some prime $p$ and some (necessarily odd) $k > 1$? Thanks in advance.
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Extrema of the Ratio of Consecutive Primes

Let $p_i$ denote the $i$th prime number. We know that $\frac{p_{n+1}}{p_n}\rightarrow 1$ as $n\rightarrow\infty$. Therefore, if we pick some real number $c>1$, there should be some positive integer ...
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(p-1)! number theory problem

I was working on this little problem: Let $\frac{a}{(p-1)!} = 1 + 1/2 + 1/3 + ... + 1/(p-1)$, where p is a positive prime. (a) Prove $p\mid a$. (b) Can $p^2 \mid a$? I thought (a) was pretty ...
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Prove that $512^3 + 675^3 + 720^3$ is a composite number

We have to prove that the number $$N=512^3 + 675^3 + 720^3$$ is composite. I tried to use the identity $(a^3+b^3+c^3)=(a+b+c)(a^2+b^2+c^2-ab-bc-ca)+3abc$ hoping to take out some common ...
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1-to-1 correspondence between twin primes and $n^2-1$

I am trying to establish the one-to-one correspondence of twin primes to integers $n$ where $n^2-1$ has 4 divisors. It is clear to me that this is the case, since $$n^2-1=(n+1)(n-1)$$ where the RHS ...
Proof that there are infinitely many primes of the form $6k+1$. Proof verification
Theorem. there are infinitely many primes of the form $6k+1$. I've just proved that there are infinitely many primes of the form $6k+1$. Could you please check my proof? At first, I proved that ...