A366657 Sum of the divisors of 8^n+1.

3, 13, 84, 800, 4356, 51792, 351120, 3100240, 17041416, 211053040, 1494039792, 12611914848, 73234343952, 794382536272, 5936210280000, 60037292774400, 282937726148616, 3264911394064320, 24128875076496960, 208532141890460960, 1225825603154905104

Offset: 0

Author

Sean A. Irvine, Oct 15 2023

Keywords

• nonn

Examples

			a(4)=4356 because 8^4+1 has divisors {1, 17, 241, 4097}.
		

Links

• Max Alekseyev, Table of n, a(n) for n = 0..502

Crossrefs

Cf. A062395, A000203, A057936, A274905, A366653, A366655, A366656, A366658.

Cf. A069061, A366578, A366607, A366617, A366629, A366638, A366666, A366668, A366689, A366715.

Programs

Maple

a:=n->numtheory[sigma](8^n+1):
seq(a(n), n=0..100);

Mathematica

DivisorSigma[1, 8^Range[0,20]+1] (* Paul F. Marrero Romero, Nov 19 2023 *)

Formula

a(n) = sigma(8^n+1) = A000203(A062395(n)).

a(n) = A069061(3*n). - Max Alekseyev, Jan 09 2024