We say a sequence $𝓢 = (sₙ)_{n≥0}$ is primefree if |sₙ| is not prime for all n ≥ 0, and to rule out trivial situations, we require that no single prime divides all terms of 𝓢. In this article, we focus on the particular Lucas sequences of the first kind, ${𝓤}_a=(uₙ)_{n≥0}$, defined by u₀ = 0, u₁ = 1, and uₙ = au_{n-1} + u_{n-2} for n≥2, where a is a fixed integer. More precisely, we show that for any integer a, there exist infinitely many integers k such that both of the shifted sequences $𝓤_a ± k$ are simultaneously primefree. This result extends previous work of the author for the single shifted sequence $𝓤_a - k$ when a = 1 to all other values of a, and establishes a weaker form of a conjecture of Ismailescu and Shim. Moreover, we show that there are infinitely many values of k such that every term of both of the shifted sequences $𝓤_a ± k$ has at least two distinct prime factors.
2
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Let $f(x) = xⁿ + k_{n-1}x^{n-1} + k_{n-2}x^{n-2} + ⋯ +k₁x + k₀ ∈ ℤ[x]$, where $3 ≤ k_{n-1} ≤ k_{n-2} ≤ ⋯ ≤ k₁ ≤ k₀ ≤ 2k_{n-1} - 3$. We show that f(x) and f(x²) are irreducible over ℚ. Moreover, the upper bound of $2k_{n-1} - 3$ on the coefficients of f(x) is the best possible in this situation.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.