%I

%S 1,2,4,6,11,20,27

%N Number of distinct prime factors of 3^(3^n)+1.

%C The term omega(3^(3^6)+1) was obtained with ECM factoring.

%F a(n) = A001221(A129290(n)).

%t Table[PrimeNu[3^(3^n) + 1], {n,1,10}] (* _G. C. Greubel_, May 16 2017 *)

%o (PARI) for(x=1,6,print1( omega(3^(3^x)+1),","))

%K hard,more,nonn

%O 0,2

%A _Jorge Coveiro_, Jan 29 2006