English

Supercongruences involving Lucas sequences

Number Theory 2020-12-15 v8

Abstract

For A,BZA,B\in\mathbb Z, the Lucas sequence un(A,B) (n=0,1,2,)u_n(A,B)\ (n=0,1,2,\ldots) are defined by u0(A,B)=0u_0(A,B)=0, u1(A,B)=1u_1(A,B)=1, and un+1(A,B)=Aun(A,B)Bun1(A,B)u_{n+1}(A,B) = Au_n(A,B)-Bu_{n-1}(A,B) (n=1,2,3,).(n=1,2,3,\ldots). For any odd prime pp and positive integer nn, we establish the new result upn(A,B)(A24Bp)un(A,B)pnZp,\frac{u_{pn}(A,B) - (\frac{A^2-4B}p) u_n(A,B)}{pn} \in \mathbb Z_p, where (p)(\frac{\cdot}p) is the Legendre symbol and Zp\mathbb Z_p is the ring of pp-adic integers. Let pp be an odd prime and let nn be a positive integer. For any integer m≢0(modp)m\not\equiv0\pmod p, we show that 1pn(k=0pn1(2kk)mk(Δp)r=0n1(2rr)mr)Zp\frac1{pn}\bigg(\sum_{k=0}^{pn-1} \frac{\binom{2k}k}{m^k} -\left(\frac{\Delta}p\right) \sum_{r=0}^{n-1}\frac{\binom{2r}r}{m^r}\bigg)\in\mathbb Z_p and furthermore 1n(k=0pn1(2kk)mk(Δp)r=0n1(2rr)mr)(2n1n1)mn1up(Δp)(m2,1)(modp2)\frac1n\bigg(\sum_{k=0}^{pn-1} \frac{\binom{2k}k}{m^k} -\left(\frac{\Delta}p\right) \sum_{r=0}^{n-1}\frac{\binom{2r}r}{m^r}\bigg)\equiv \frac{\binom{2n-1}{n-1}}{m^{n-1}} u_{p-(\frac{\Delta}p)}(m-2,1) \pmod{p^2} where Δ=m(m4)\Delta=m(m-4). We also pose some conjectures for further research.

Keywords

Cite

@article{arxiv.1610.03384,
  title  = {Supercongruences involving Lucas sequences},
  author = {Zhi-Wei Sun},
  journal= {arXiv preprint arXiv:1610.03384},
  year   = {2020}
}

Comments

26 pages, refined version

R2 v1 2026-06-22T16:17:48.267Z