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 A366666 #13 Jan 08 2024 20:59:47
%S A366666 3,18,126,1332,10476,109926,816732,8906760,64570086,706911048,
%T A366666 5357742012,56496274632,456919958880,4661686010664,35152280388792,
%U A366666 388532214509688,2779530283277766,30018958465575240,230668806145962744,2431533550553980488,19410628990783168944
%N A366666 Sum of the divisors of 9^n+1.
%H A366666 Max Alekseyev, <a href="/A366666/b366666.txt">Table of n, a(n) for n = 0..345</a>
%F A366666 a(n) = sigma(9^n+1) = A000203(A062396(n)).
%F A366666 a(n) = A366578(2*n). - _Max Alekseyev_, Jan 08 2024
%e A366666 a(2)=126 because 9^2+1 has divisors {1, 2, 41, 82}.
%p A366666 a:=n->numtheory[sigma](9^n+1):
%p A366666 seq(a(n), n=0..100);
%t A366666 DivisorSigma[1, 9^Range[0,20] + 1] (* _Paul F. Marrero Romero_, Nov 14 2023 *)
%Y A366666 Cf. A062396, A000203, A057935, A366662, A366664, A366665, A366667.
%Y A366666 Cf. A069061, A366578, A366607, A366617, A366629, A366638, A366657, A366668, A366689, A366715.
%K A366666 nonn
%O A366666 0,1
%A A366666 _Sean A. Irvine_, Oct 15 2023