A366634 Sum of the divisors of 7^n-1.

12, 124, 780, 7812, 33624, 354640, 1704240, 18929096, 97036800, 800520192, 3958188480, 56928231360, 193778020824, 1830926384640, 11181115146240, 115997032277280, 465294239722800, 5175558387507200, 22852200371636160, 287850454432579584, 1318081737957660000

Offset: 1

Author

Sean A. Irvine, Oct 14 2023

Keywords

• nonn

Examples

			a(5)=33624 because 7^5-1 has divisors {1, 2, 3, 6, 2801, 5602, 8403, 16806}.
		

Links

• Max Alekseyev, Table of n, a(n) for n = 1..388

Crossrefs

Cf. A024075, A000203, A057954, A059887, A074249, A218358, A366632, A366633, A366635.

Cf. A075708, A366576, A366603, A366613, A366622, A366653, A366662, A102146, A366684, A366710.

Programs

Maple

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

Mathematica

DivisorSigma[1, 7^Range[30]-1]

Formula

a(n) = sigma(7^n-1) = A000203(A024075(n)).