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 A366689 #9 Jun 22 2025 15:25:45
%S A366689 3,28,186,3458,21966,375816,2911272,45470096,340452396,6278429920,
%T A366689 39543942612,706019328000,4708961513592,82162955169792,
%U A366689 599236951715280,11195197038864384,68925937595777100,1179397832668228992,9136813499663186064,144079834776308121600
%N A366689 Sum of the divisors of 11^n+1.
%H A366689 Max Alekseyev, <a href="/A366689/b366689.txt">Table of n, a(n) for n = 0..325</a>
%F A366689 a(n) = sigma(11^n+1) = A000203(A034524(n)).
%e A366689 a(4)=21966 because 11^4+1 has divisors {1, 2, 7321, 14642}.
%p A366689 a:=n->numtheory[sigma](11^n+1):
%p A366689 seq(a(n), n=0..100);
%t A366689 DivisorSigma[1,11^Range[0,20]+1] (* _Harvey P. Dale_, Jun 22 2025 *)
%Y A366689 Cf. A034524, A000203, A366666, A366684, A366686, A366687, A366688, A366690, A366715.
%K A366689 nonn
%O A366689 0,1
%A A366689 _Sean A. Irvine_, Oct 16 2023