A366709 - OEIS

%I #7 Jan 04 2024 13:39:36

%S 2,4,4,16,4,32,8,64,16,16,12,256,8,64,64,512,8,512,4,192,32,48,16,

%T 4096,16,192,64,1024,32,8192,32,2048,192,64,512,16384,8,64,128,12288,

%U 16,12288,32,3072,4096,256,8,262144,32,1024,64,6144,128,65536,192,8192

%N Number of divisors of 12^n-1.

%H Max Alekseyev, <a href="/A366709/b366709.txt">Table of n, a(n) for n = 1..310</a>

%F a(n) = sigma0(12^n-1) = A000005(A024140(n)).

%e a(3)=4 because 12^3-1 has divisors {1, 11, 157, 1727}.

%p a:=n->numtheory[tau](12^n-1):

%p seq(a(n), n=1..100);

%t DivisorSigma[0, 12^Range[100]-1]

%o (PARI) a(n) = numdiv(12^n-1);

%Y Cf. A000005, A024140, A046801, A070528, A366707, A366708, A366710, A366683.

%K nonn

%O 1,1

%A _Sean A. Irvine_, Oct 17 2023