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 A347883 #10 Sep 19 2021 13:04:47 %S A347883 2,2,1,0,0,1,2,0,1,2,2,2,2,0,2,0,1,1,2,0,2,2,0,2,0,0,2,1,2,0,1,1,1,2, %T A347883 2,2,2,0,2,2,0,2,2,2,2,2,2,2,0,2,0,1,1,1,2,2,2,2,0,2,2,0,2,0,2,0,2,1, %U A347883 2,2,1,2,2,0,2,1,0,2,1,0,1,2,2,1,2,0,1,2,1,0,2,0,1,2,2,0,1,1,1,1,2,0,1,2,1 %N A347883 a(n) = A342926(n) mod 3. %H A347883 Antti Karttunen, <a href="/A347883/b347883.txt">Table of n, a(n) for n = 1..65537</a> %F A347883 a(n) = A342926(n) mod 3. %t A347883 ad[1] = 0; ad[n_] := n * Total@(Last[#]/First[#]& /@ FactorInteger[n]); a[n_] := Mod[ad[DivisorSigma[1, n]] - n, 3]; Array[a, 105] (* _Amiram Eldar_, Sep 18 2021 *) %o A347883 (PARI) %o A347883 A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1])); %o A347883 A342926(n) = (A003415(sigma(n))-n); %o A347883 A347883(n) = (A342926(n)%3); %Y A347883 Cf. A000203, A003415, A342926, A347880 (positions of zeros). %Y A347883 Cf. also A347871. %K A347883 nonn %O A347883 1,1 %A A347883 _Antti Karttunen_, Sep 18 2021