OFFSET
1,1
COMMENTS
Odd numbers k such that gcd(k,2^(k-1)-1) = 1 and gcd(k,3^(k-1)-1) > 1.
It seems that a(n) == 91 (mod 156) for infinitely many n.
Fermat pseudoprimes to base 3 (A005935) in this sequence are 16531, 49051, 72041, ...
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MAPLE
select(k->gcd(k, 2^k-2) = 1 and gcd(k, 3^k-3) > 1, [$1..10000]); # Muniru A Asiru, Oct 07 2018
MATHEMATICA
Select[Range[8000], GCD[#, 2^# - 2] == 1 && GCD[#, 3^# - 3] > 1 &] (* Amiram Eldar, Mar 31 2024 *)
PROG
(PARI) isok(k) = (gcd(k, 2^k-2) == 1) && (gcd(k, 3^k-3) != 1); \\ Michel Marcus, Aug 14 2018
(GAP) Filtered([1..10000], k->Gcd(k, 2^k-2) = 1 and Gcd(k, 3^k-3) > 1); # Muniru A Asiru, Oct 07 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Thomas Ordowski, Aug 14 2018
EXTENSIONS
More terms from Michel Marcus, Aug 14 2018
STATUS
approved