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 A121278 #9 Oct 16 2023 04:31:08
%S A121278 1,3,5,3,13,9,19,5,15,15,51,9,73,30,65,9,113,21,163,9,25,63,265,15,65,
%T A121278 57,45,30,281,45,391,17,255,123,247,21,577,165,65,15,841,27,757,63,
%U A121278 195,234,1105,27,133,75,565,30,1249,57,65,50,95,339,929,27,1321,408,75,33,949
%N A121278 Number of distinct integers of the form (x^n + y^n) mod n^2.
%C A121278 It is enough to take x,y from {0,1,...,n-1}. Therefore a(n)<=n*(n+1)/2.
%o A121278 (PARI) { a(n) = my(S, t); S=Set(); for(x=0,n-1, for(y=x,n-1, t=lift(Mod(x,n^2)^n+Mod(y,n^2)^n); S=setunion(S,[t]); ); ); #S }
%o A121278 (PARI) a(n) = #setbinop((x, y)->Mod(x, n^2)^n+Mod(y, n^2)^n, [0..n-1]); \\ _Michel Marcus_, Oct 16 2023
%K A121278 nonn
%O A121278 1,2
%A A121278 _Max Alekseyev_, Aug 23 2006
%E A121278 More terms from _Michel Marcus_, Oct 16 2023