A366683 Number of divisors of 11^n-1.

4, 16, 16, 40, 12, 192, 16, 96, 32, 96, 16, 1920, 16, 128, 96, 448, 8, 1024, 8, 480, 768, 1024, 32, 18432, 128, 512, 64, 2560, 16, 9216, 32, 2048, 512, 256, 192, 20480, 64, 512, 4096, 4608, 512, 36864, 16, 10240, 384, 2048, 32, 1376256, 128, 4096, 512, 2560

Offset: 1

Author

Sean A. Irvine, Oct 16 2023

Keywords

• nonn

Examples

			a(3)=16 because 11^3-1 has divisors {1, 2, 5, 7, 10, 14, 19, 35, 38, 70, 95, 133, 190, 266, 665, 1330}.
		

Links

• Max Alekseyev, Table of n, a(n) for n = 1..316

Crossrefs

Cf. A024127, A000005, A366681, A366682, A366684, A366685.

Cf. A046801, A070528, A366709.

Programs

Maple

a:=n->numtheory[tau](11^n-1):
seq(a(n), n=1..100);

Mathematica

DivisorSigma[0, 11^Range[100]-1]

PARI

a(n) = numdiv(11^n-1);

Formula

a(n) = sigma0(11^n-1) = A000005(A024127(n)).