English

Cullen and Woodall numbers in Padovan and Perrin sequences

Number Theory 2026-05-25 v1

Abstract

Let {Pn}n0\{P_n\}_{n\ge 0} and {Rn}n0\{R_n\}_{n\ge 0} denote the Padovan and Perrin sequences, both satisfying the recurrence Un+3=Un+1+UnU_{n+3} = U_{n+1} + U_n, but with initial values P0=P1=P2=1P_0 = P_1 = P_2 = 1 and R0=3R_0 = 3, R1=0R_1 = 0, R2=2R_2 = 2, respectively. A \textit{Cullen number} is a positive integer of the form m2m+1m\cdot 2^m + 1 for some integer m1m \ge 1, while a \textit{Woodall number} is a positive integer of the form m2m1m\cdot 2^m - 1 for some integer m1m \ge 1. In this paper, we determine all Woodall numbers in the Padovan sequence and all Cullen numbers in the Perrin sequence. Specifically, we prove that 11 and 77 are the only Woodall numbers in the Padovan sequence, and that 33 is the only Cullen number in the Perrin sequence.

Keywords

Cite

@article{arxiv.2605.23084,
  title  = {Cullen and Woodall numbers in Padovan and Perrin sequences},
  author = {Herbert Batte and Eric F. Bravo and Florian Luca},
  journal= {arXiv preprint arXiv:2605.23084},
  year   = {2026}
}

Comments

20 pages