A366637 Number of divisors of 7^n+1.

2, 4, 6, 8, 4, 16, 24, 16, 8, 16, 32, 16, 32, 16, 12, 64, 8, 8, 48, 16, 16, 128, 48, 8, 16, 32, 24, 32, 64, 8, 512, 32, 16, 128, 48, 1024, 256, 16, 12, 256, 64, 64, 96, 512, 32, 2048, 96, 8, 64, 2048, 640, 128, 32, 64, 384, 3072, 256, 256, 96, 64, 512, 8, 48

Offset: 0

Author

Sean A. Irvine, Oct 15 2023

Keywords

• nonn

Examples

			a(4)=4 because 7^4+1 has divisors {1, 2, 1201, 2402}.
		

Links

• Max Alekseyev, Table of n, a(n) for n = 0..387

Crossrefs

Cf. A034491, A000005, A057937, A227575, A366633, A366636, A366638, A366639.

Cf. A046798, A366577, A366606, A366616, A366628, A366656, A366665, A344897, A366688, A366714.

Programs

Maple

a:=n->numtheory[tau](7^n+1):
seq(a(n), n=0..100);

Mathematica

DivisorSigma[0, 7^Range[0, 62] + 1] (* Paul F. Marrero Romero, Oct 16 2023 *)

PARI

a(n) = numdiv(7^n+1);

Formula

a(n) = sigma0(7^n+1) = A000005(A034491(n)).