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 A366638 #12 Jan 20 2024 12:24:09
%S A366638 3,15,93,660,3606,34560,236964,1559520,9155916,77423280,530807472,
%T A366638 3868683120,21224771760,185094572580,1261494915594,9988783073280,
%U A366638 49990612274316,436182213726030,3279858902194056,21372989348391720,122709716651985624,1082323574100172800
%N A366638 Sum of the divisors of 7^n+1.
%H A366638 Max Alekseyev, <a href="/A366638/b366638.txt">Table of n, a(n) for n = 0..387</a>
%F A366638 a(n) = sigma(7^n+1) = A000203(A034491(n)).
%e A366638 a(4)=3606 because 7^4+1 has divisors {1, 2, 1201, 2402}.
%p A366638 a:=n->numtheory[sigma](7^n+1):
%p A366638 seq(a(n), n=0..100);
%t A366638 DivisorSigma[1, 7^Range[0, 21] + 1] (* _Paul F. Marrero Romero_, Oct 16 2023 *)
%Y A366638 Cf. A034491, A000203, A057937, A227575, A366634, A366636, A366637, A366639.
%Y A366638 Cf. A069061, A366578, A366607, A366617, A366629, A366657, A366666, A366668, A366689, A366715.
%K A366638 nonn
%O A366638 0,1
%A A366638 _Sean A. Irvine_, Oct 15 2023