OFFSET
1,3
COMMENTS
From Jianing Song, Mar 02 2021: (Start)
2^(a(n)+1) is the multiplicative order of 2 modulo A023394(n).
Each k occurs A046052(k) times in this sequence provided that F(k) = 2^2^k + 1 is squarefree (no counterexamples are known). (End)
Alternatively, a(n) is the only k such that A023394(n) divides A000215(k). - Lorenzo Sauras Altuzarra, Feb 01 2023
LINKS
Wilfrid Keller, Prime factors k.2^n + 1 of Fermat numbers F_m
Lorenzo Sauras-Altuzarra, Some properties of the factors of Fermat numbers, Art Discrete Appl. Math. (2022).
PROG
(PARI) forprime(p=3, , r=znorder(Mod(2, p)); hammingweight(r)==1&&print1(logint(r, 2)-1, ", ")) \\ Jeppe Stig Nielsen, Mar 04 2018
CROSSREFS
KEYWORD
nonn,more
AUTHOR
EXTENSIONS
STATUS
approved