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 A366819 #12 Jul 04 2024 03:36:34 %S A366819 4,42,432,6048,67584,1704240,38054016,967814400,16203253248, %T A366819 513593801496,15743437516800,720045832568832,19146847615988736, %U A366819 835966563470742528,31421980989189888768,1602925310146310674200,52064744760120508416000,4286575920597346109768658 %N A366819 a(n) is the sum of the divisors of n^n-1. %H A366819 Amiram Eldar, <a href="/A366819/b366819.txt">Table of n, a(n) for n = 2..138</a> %F A366819 a(n) = A000203(A048861(n)). %t A366819 Array[DivisorSigma[1, #^# - 1] &, 18, 2] (* _Michael De Vlieger_, Oct 24 2023 *) %o A366819 (PARI) a(n) = sigma(n^n-1); %Y A366819 Cf. A000203, A048861, A309941, A344870, A334167, A062727, A366820. %K A366819 nonn %O A366819 2,1 %A A366819 _Sean A. Irvine_, Oct 24 2023