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 A290321 #10 Aug 03 2017 04:34:45
%S A290321 1,2,0,0,5,1,0,6,0,0,4,1,8,5,0,0,15,1,0,8,0,0,8,0,14,18,16,0,20,1,0,
%T A290321 11,0,25,12,1,20,14,0,0,8,1,0,15,0,0,16,7,0,17,28,0,45,0,32,20,0,0,40,
%U A290321 1,32,24,0,30,44,1,0,23,60,0,24,1,38,25,40,66,14,1
%N A290321 Sum modulo n of all units u in Z/nZ such that Phi(3,u) is a unit, where Phi is the cyclotomic polynomial.
%p A290321 with(numtheory): m:=3: for n from 2 to 100 do S:={}: for a from 1 to n-1 do if gcd(a,n)=1 and gcd(cyclotomic(m,a),n)=1 then S:={op(S),a}: fi: od: print(sum(op(i,S),i=1..nops(S)) mod n): od:
%t A290321 Table[Mod[Total@ Select[Range[n - 1], CoprimeQ[#, n] && CoprimeQ[Cyclotomic[3, #], n] &], n], {n, 79}] (* _Michael De Vlieger_, Jul 29 2017 *)
%o A290321 (PARI) a(n) = sum(k=0, n-1, k*((gcd(n, k)==1) && (gcd(n, polcyclo(3, k))==1))) % n; \\ _Michel Marcus_, Jul 29 2017
%Y A290321 Cf. A058026, A289460.
%K A290321 nonn
%O A290321 2,2
%A A290321 _Michael Mueller_, _Jordan Lenchitz_, _Tristan Phillips_, _Madison Wellen_, _Eric Jovinelly_, _Joshua Harrington_, Jul 27 2017