共 112 个问题,第 6/6 页
Prove that every value in the range of the divisor function is the sum of two other numbers in that range.
Is the following statement true or false?Let $\mathbb{N}$ be the set of positive integers. For any $z > 2$, there always exist $x, y < z$ such that:$$f(x) + f(y) = f(z)$$Where the arithmetic function $f(n)$ is defined as:$$f(n) = \prod_{p^k \parallel n} \left( \frac{p^{k+1}-1}{p-1} \right) =...
How did they find $x^3+y^3+z^3 = 165$ which has a larger solution than $x^3+y^3+z^3 = 33$?
The discovery by Andrew Booker of an integer solution to, $$N=x^3 + y^3 +z^3=33$$ $$8866128975287528^3 - 8778405442862239^3 -2736111468807040^3=33$$ got some press and Youtube mileage back in 2019. As mentioned in Booker's July 2019 article, for $0<N<1000$, there used to be $13$ unsolved $N$,...
Reference request: Proof of the non-existence of three consecutive perfect powers
I am looking for a reference—either a book or a specific paper—that contains the actual proof of the result that no three consecutive positive integers are perfect powers. While reading Wacław Sierpiński's 250 Problems in Elementary Number Theory, I came across a remark stating that A. Mąkowski...
What's so special about the digit 6 here?
I ran a simulation where for each 2-digit combination with 30 symbols (so 0 to T), it checked, from base 2 to base 10,000, in how many bases that specific symbol combination resulted in a prime number. The top 10 were 65,6B,6H,6T,6N,61,6D,67,6J, and 6P. All starting with 6. Anyone have any idea...
Rational number or transcendental number, but not algebraic irrational number
Let P(n) and Q(n) be two non-trivial polynomials in n with rational coefficients and z[P, Q] is the value of infinite sum of P(n)/Q(n) from n=1 to +∞ (only when it converges, in which the degree of Q should be larger than or equal to the degree of P plus 2). Claim: It is impossible for z[P,Q] to...
An infinite family of prime-free quadratic sequences from the transposed triangular grid
Background The triangular grid places integer $T(r-1)+c$ at row $r$, column $c$, where $T(n)=n(n+1)/2$. Transposing this grid, reading along SE diagonals of the triangular grid as columns, yields a new array whose column $d$ has values $$f_d(n) = T(n+d-2)+n = \frac{n^2+(2d-1)n+(d-1)(d-2)/2 + ......
Exploring prime factorization disorder as a signal for nearby primes
About prime factorization of consecutive integers, we all can notice prime factors vary apparently without any logic. Some numbers like $82 = 2 \times 41$ have highly unequal factors (high variance among the factors), while others like $80 = 2^4 \times 5$ or $2310 = 2 \times 3 \times 5 \times 7...
An estimate for multiplicative function
Given a multiplicative function $f$ with divisor bound $|f|\le \tau_k$, where $k$ is a nonnegative real number. We consider the Dirichlet series $$ F(s)=\sum_{n=1}^\infty \dfrac{f(n)}{n^s}. $$ Since $$ \sum_{n=1}^\infty \dfrac{\tau_k(s)}{n^s}=\zeta(s)^k, $$ $F(s)$ absolutely converges on the...
What extra state data is needed to make this affine-family transition deterministic?
Consider affine families $$ Q(u)=2^t3^{16}u+B, $$ with $t\ge 3$ and $2^t\mid 3B-1$. Set $$ C_0=\frac{3B-1}{2^t}. $$ Then $$ 3Q(u)-1 =2^t3^{17}u+(3B-1) =2^t(3^{17}u+C_0). $$ Suppose we restrict to a subfamily where, after the fixed factor $2^t$, another $2^\lambda$ divides the remaining factor:...
Is the Seive of Eratosthens a Breadth First Search Algorithm?
Numbers that are not yet mapped to are marked prime and given their own "trees", but really they are distance $\infty$ from the other primes. Traditionally, in a connected graph, BFS forms one tree, but really this is a collection of overlapping trees. What we have on the number line is a...
iterated forward difference operator applied to primes, OEIS A007442
I apply the iterated forward difference operator to the sequence of primes; from $$ (p_n) = (2, 3, 5, 7, 11 \ldots) $$ I get $$ (d^1_n) = (1, 2, 2, 4 \ldots) $$ $$ (d^2_n) = (1, 0, 2 \ldots) $$ $$ (d^3_n) = (-1, 2 \ldots) $$ $$ \ldots $$ For each sequence $(x_n)$, one can reconstruct the...
Minimum value of $i$ to change $\lfloor n / i \rfloor$
I was solving this CSES question called Sum of Divisors and one of the solutions in the USACO Guide hints at this statement: The minimum value of $j > i$ such that $\lfloor n/j \rfloor$ < $\lfloor n/i \rfloor$ is $j = \lfloor n/q \rfloor + 1$, where $q = \lfloor n/i \rfloor$ for integers $j, i...
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