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 A330069 #29 Feb 27 2020 05:57:37
%S A330069 1,4,60,1716,3444,132396,4428816612,48846257124
%N A330069 Numbers k such that Sum_{i=1..k} i^A000010(k) == -2 (mod k).
%C A330069 Apparently includes the sequence 2*A007850.
%C A330069 Additional terms include 4428816612, 48846257124, 865498410347676, 29474266940021148, 1101686782618260636, 488394001964999430175732692, 1108159829234141602577157118356, 3821334362841015969111519832677012.
%C A330069 a(9) > 10^13. - _Giovanni Resta_, Feb 27 2020
%t A330069 G[n_, k_] := G[n, k] = Mod[Sum[PowerMod[i, k, n], {i, 1, n}], n];
%t A330069 Select[Range[2000], G[#, EulerPhi[#]] == n-2 &]
%t A330069 fa=FactorInteger;
%t A330069 se[n_, k_] := Select[Transpose[fa[n]][[1]], IntegerQ[k/(# - 1)] &];
%t A330069 sumlis[li_] := Sum[li[[i]], {i, 1, Length[li]}]
%t A330069 Table[If[Mod[-n/se[n, EulerPhi[n]] // sumlis, n] == n-2, n], {n, 1,
%t A330069 1000000}] // Union
%o A330069 (PARI) isok(n) = sumdiv(n, d, eulerphi(n/d) * Mod(d, n)^eulerphi(n)) == -2; \\ _Daniel Suteu_, Jan 13 2020
%Y A330069 Cf. A000010, A054377, A007850, A330068.
%K A330069 nonn,hard,more
%O A330069 1,2
%A A330069 _José María Grau Ribas_, Nov 30 2019
%E A330069 a(7)-a(8) from _Giovanni Resta_, Feb 27 2020