%I A133801
%S A133801 1,1,2,2,2,3,2,3,3,3,3,5,2,3,4,5,3,6,3,5,4,5,3,7,4,3,6,6,4,8,4,6,5,6,5,
%T A133801 9,3,5,6,7,4,8,3,8,8,4,5,12,7,7,6,6,4,11,6,9,7,7,3,12,3,6,6,7,6,10,4,9,
%U A133801 6,8,2,12,5,6,9,8,7,12,4,11,9,6,5,14,6,4,8,12,4,16,5,7,7,8,6,15,4,10,8
%N A133801 Number of distinct prime divisors of 3^n - 1.
%D A133801 Eric Weisstein's World of Mathematics, "Prime Factor", http://mathworld.wolfram.com/
               PrimeFactor.html
%F A133801 a(n) = omega(3^n - 1) = A001221(3^n - 1)
%e A133801 a(4) = omega(3^4 - 1) = omega(80) = omega(2^4 * 5) = 2.
%o A133801 (PARI) for(n = 1, 100, print1(omega(3^n - 1), ", "))
%Y A133801 Cf. A113913.
%Y A133801 Sequence in context: A076869 A104307 A128330 this_sequence A112310 A137734 
               A078705
%Y A133801 Adjacent sequences: A133798 A133799 A133800 this_sequence A133802 A133803 
               A133804
%K A133801 nonn
%O A133801 1,3
%A A133801 Ryan Propper (rpropper(AT)cs.stanford.edu), Jan 06 2008