English

On the sum of a prime and two Fibonacci numbers

Number Theory 2025-06-05 v1

Abstract

Let {fn}\{f_n\} be the Fibonacci sequence. For any positive integer nn, let r(n)r(n) be the number of solutions of n=p+fk12+fk22n=p+f_{k_1^{2}} +f_{k_{2}^{2}}, where pp is a prime and k1,k2k_1, k_2 are nonnegative integers with k1k2k_1\le k_2. In this paper, it is proved that {n:r(n)=0}\{ n : r(n)=0\} contains an infinite arithmetic progression, and both sets {n:r(n)=1}\{ n : r(n)=1\} and {n:r(n)2}\{ n : r(n)\ge 2\} have positive asymptotic densities.

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Cite

@article{arxiv.2506.03631,
  title  = {On the sum of a prime and two Fibonacci numbers},
  author = {Ji-Zhen Xu and Yong-Gao Chen},
  journal= {arXiv preprint arXiv:2506.03631},
  year   = {2025}
}

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21 pages