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 A228926 #17 Feb 15 2023 13:51:36
%S A228926 0,1,2,0,0,3,0,0,6,5,0,0,0,7,7,0,0,9,0,0,14,11,0,0,0,13,18,0,0,15,0,0,
%T A228926 22,17,23,0,0,19,26,0,0,21,0,0,30,23,0,0,0,25,34,0,0,27,44,0,38,29,0,
%U A228926 0,0,31,42,0,0,33,0,0,46,35,0,0,0,37,35,0,66
%N A228926 Sum(m^(n+1), m=1...n-1) modulo n.
%H A228926 Antti Karttunen, <a href="/A228926/b228926.txt">Table of n, a(n) for n = 1..16384</a>
%F A228926 a(n) = A121706(n) mod (n-1). - _T. D. Noe_, Sep 16 2013
%t A228926 f[n_] := Mod[Sum[PowerMod[i,n+1,n], {i, 1, n}], n]; Table[f[n], {n, 100}]
%o A228926 (PARI) a(n)=lift(sum(m=1,n-1,Mod(m,n)^(n+1))) \\ _Charles R Greathouse IV_, Dec 27 2013
%Y A228926 Cf. A121706, A228919, A204187.
%K A228926 nonn
%O A228926 1,3
%A A228926 _José María Grau Ribas_, Sep 08 2013