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For questions related to 'elementary' proofs in a technical sense, which has nothing to do with the difficulty of the argument or result. A typical example would be 'elementary' proofs of the Prime Number Theorem, which avoid complex analysis. The tag is however not limited to this particular notion of 'elementary.'

1 vote
0 answers
93 views

Primality test for specific class of $N=12k \cdot 5^n-1$

Can you provide a proof for the following claim: Let $P_m(x)=2^{-m}\cdot \left(\left(x-\sqrt{x^2-4})^m+(x+\sqrt{x^2-4}\right)^m\right)$ . Let $N= 12k \cdot 5^{n} - 1 $ where $n\ge3$ , $12k <5^n$ a …
Pedja's user avatar
  • 2,661
9 votes
1 answer
686 views

An infinite series involving harmonic numbers

I am looking for a proof of the following claim: Let $H_n$ be the nth harmonic number. Then, $$\frac{\pi^2}{12}=\ln^22+\displaystyle\sum_{n=1}^{\infty}\frac{H_n}{n(n+1) \cdot 2^n}$$ The SageMath cel …
Pedja's user avatar
  • 2,661
4 votes
1 answer
321 views

Primality test for $N=2^mp^n +1$

This question is related to my previous question. Can you prove or disprove the following claim: Let $N=2^mp^n+1$ , $m>0 , n>0$ and $p$ is an odd prime . If there exists an integer $a$ such that $$\d …
Pedja's user avatar
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0 votes
0 answers
123 views

Testing the primality of Mersenne and Fermat numbers using third order recurrence relation

Can you prove or disprove the claims given below? Inspired by generalization of Lucas-Lehmer test I have formulated the following claims: Claim 1 Let $M_p=2^p-1$ where $p$ is an odd prime number , le …
Pedja's user avatar
  • 2,661
7 votes
1 answer
460 views

Primality test for $N=2^a3^b+1$

Can you prove or disprove the following claim: Let $N=2^a3^b+1$ , $a>0 , b>0$ . If there exists an integer $c$ such that $$c^{(N-1)/3}-c^{(N-1)/6} \equiv -1 \pmod{N}$$ then $N$ is a prime. You can r …
Pedja's user avatar
  • 2,661
7 votes
2 answers
453 views

An infinite series involving the mod-parity of Euler's totient function

Can you prove or disprove the following claim: First, define the function $\xi(n)$ as follows: $$\xi(n)=\begin{cases}-1, & \text{if }\varphi(n) \equiv 0 \pmod{4} \\ 1, & \text{if }\varphi(n) \equiv 2 …
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14 votes
4 answers
1k views

Six points on an ellipse

Can you prove the following proposition: Proposition. Let $\triangle ABC$ be an arbitrary triangle with centroid $G$. Let $D,E,F$ be the points on the sides $AC$,$AB$ and $BC$ respectively , such tha …
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3 votes
2 answers
270 views

Four concyclic points inside bicentric quadrilateral

Can you provide a proof for the following proposition: Proposition. Let quadrilateral $ABCD$ be inscribed into a circle with center $O$ and circumscribed around a circle with center $I$. Let $X$ be a …
Pedja's user avatar
  • 2,661
12 votes
2 answers
656 views

A conjectural infinite series for $\frac{\pi^2}{5\sqrt{5}}$

I am looking for a proof of the following claim: First define the function $\chi(n)$ as follows: $$\chi(n)=\begin{cases}1, & \text{if }n \equiv \pm 1 \pmod{10} \\ -1, & \text{if }n \equiv \pm 3 \pmod{ …
Pedja's user avatar
  • 2,661
1 vote
0 answers
116 views

A primality criterion for specific class of $N=4kp^n+1$

Can you provide a proof for the following claim: Let $P_m(x)=2^{-m}\cdot \left(\left(x-\sqrt{x^2-4})^m+(x+\sqrt{x^2-4}\right)^m\right)$ . Let $N= 4kp^n+1 $ such that $p$ is a prime number greater tha …
Pedja's user avatar
  • 2,661
3 votes
1 answer
383 views

Primality test for specific class of $N=k \cdot b^n-1$

This question is successor of Compositeness test for specific class of $N=k \cdot b^n-1$ . Can you provide a proof or a counterexample to the following claim : Let $P_m(x)=2^{-m}\cdot \left(\left …
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  • 2,661
2 votes
1 answer
833 views

Primality test for generalized Fermat numbers

This question is successor of Primality test for specific class of generalized Fermat numbers . Can you provide a proof or a counterexample for the claim given below? Inspired by Lucas–Lehmer–Riesel …
Pedja's user avatar
  • 2,661
4 votes
1 answer
182 views

Primality test for specific class of $N=8k \cdot 3^n-1$

This question is related to my previous question. Can you prove or disprove the following claim: Let $P_m(x)=2^{-m}\cdot \left(\left(x-\sqrt{x^2-4}\right)^{m}+\left(x+\sqrt{x^2-4}\right)^{m}\right)$ …
Pedja's user avatar
  • 2,661
10 votes
0 answers
631 views

Primality testing using Chebyshev polynomials

Can you provide a proof or a counterexample for the claim given below? Inspired by an alternative definition of the Frobenius primality test which is given in this paper I have formulated the followin …
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  • 2,661
4 votes
1 answer
574 views

The constant $e$ represented by an infinite series

In this Wikipedia article the constant $\pi$ is represented by the following infinite series: $$\pi=1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}-\frac{1}{5}+\frac{1}{6}+\frac{1}{7}+\frac{1}{8}+\frac{1}{9}-\f …
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