A366660 - OEIS

%I #12 Jan 07 2024 13:32:09

%S 1,2,3,3,3,5,3,5,6,5,5,7,3,6,8,6,6,9,5,7,8,8,4,12,7,6,11,9,7,12,6,7,

%T 10,9,8,12,6,8,12,11,6,14,4,12,16,7,8,15,10,12,13,9,6,15,11,14,13,10,

%U 5,18,5,10,16,8,9,15,6,13,13,15,7,19,7,10,19,13,11

%N Number of distinct prime divisors of 9^n - 1.

%H Max Alekseyev, <a href="/A366660/b366660.txt">Table of n, a(n) for n = 1..690</a>

%F a(n) = omega(9^n-1) = A001221(A024101(n)).

%F a(n) = A133801(2*n) = A133801(n) + A366580(n) - 1. - _Max Alekseyev_, Jan 07 2024

%o (PARI) for(n = 1, 100, print1(omega(9^n - 1), ", "))

%Y Cf. A024101, A001221, A057952, A366661, A366662, A366663.

%Y Cf. A046800, A133801, A366604, A366611, A366620, A366632, A366651, A102347, A366681, A366707.

%K nonn

%O 1,2

%A _Sean A. Irvine_, Oct 15 2023