This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A366653 #13 Aug 02 2025 11:18:03
%S A366653 8,104,592,8736,38912,473600,2466048,38054016,155493536,2015330304,
%T A366653 10359014400,166290432000,636328345600,7645340651520,42424026529792,
%U A366653 648494317126656,2599936977797120,32817383473149440,164708609085669376,3010983668199456768
%N A366653 Sum of the divisors of 8^n-1.
%H A366653 Max Alekseyev, <a href="/A366653/b366653.txt">Table of n, a(n) for n = 1..500</a>
%F A366653 a(n) = sigma(8^n-1) = A000203(A024088(n)).
%F A366653 a(n) = A075708(3*n). - _Max Alekseyev_, Jan 09 2024
%e A366653 a(5)=38912 because 8^5-1 has divisors {1, 7, 31, 151, 217, 1057, 4681, 32767}.
%p A366653 a:=n->numtheory[sigma](8^n-1):
%p A366653 seq(a(n), n=1..100);
%t A366653 DivisorSigma[1, 8^Range[30]-1]
%o A366653 (SageMath) [sigma(8**n-1, 1) for n in range(1, 21)] # _Stefano Spezia_, Aug 02 2025
%Y A366653 Cf. A024088, A000203, A057953, A059890, A366651, A366652, A366654.
%Y A366653 Cf. A075708, A366576, A366603, A366613, A366622, A366634, A366662, A102146, A366684, A366710.
%K A366653 nonn
%O A366653 1,1
%A A366653 _Sean A. Irvine_, Oct 15 2023