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 A366820 #7 Feb 16 2025 08:34:06
%S A366820 3,3,6,56,258,6264,52136,1559520,17041416,706911048,10102223208,
%T A366820 706019328000,9101898907920,519285252355776,11672709747324912,
%U A366820 880565163670372352,18446811354131136516,1792353900753729655758,54357680125881245248800,4154723599066412190910560
%N A366820 a(n) is the sum of the divisors of n^n + 1.
%H A366820 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SierpinskiNumberoftheFirstKind.html">Sierpinski Number of the First Kind</a>
%F A366820 a(n) = A000203(A014566(n)).
%t A366820 {3}~Join~Array[DivisorSigma[1, #^# + 1] &, 19] (* _Michael De Vlieger_, Oct 24 2023 *)
%o A366820 (PARI) a(n) = sigma(n^n+1);
%Y A366820 Cf. A000203, A007571, A014566, A055385, A062727, A344859, A366819.
%K A366820 nonn
%O A366820 0,1
%A A366820 _Sean A. Irvine_, Oct 24 2023