%I #9 Jun 13 2024 07:44:09
%S 1,19,1657009,9950006745799417075771,
%T 19389268200585836264288587113776883575610248525384021488302948711030121
%N a(n) = (2^(3^n)+1)/3^(n+1).
%t Table[(2^(3^n) + 1)/3^(n + 1), {n, 6}] (* _Wesley Ivan Hurt_, Dec 26 2023 *)
%K easy,nonn
%O 1,2
%A _Benoit Cloitre_, May 13 2002
%E One more term from _Benoit Cloitre_, Nov 01 2002