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 A339448 #12 Dec 23 2020 19:52:31
%S A339448 0,2,1,1,0,2,2,0,1,1,1,0,1,1,0,2,0,2,2,2,0,1,0,2,0,1,1,0,2,2,0,1,1,1,
%T A339448 0,2,2,2,2,0,2,0,1,1,0,2,2,2,2,0,1,1,1,0,2,0,2,0,1,0,2,2,0,1,1,0,2,2,
%U A339448 2,0,1,1,1,0,1,0,2,0,1,1,0,2,2,0,1,0
%N A339448 a(n) = (prime(n) - a(n-1)) mod 3; a(0)=0.
%e A339448 a(1) = ( 2 - 0) mod 3 = 2,
%e A339448 a(2) = ( 3 - 2) mod 3 = 1,
%e A339448 a(3) = ( 5 - 1) mod 3 = 1,
%e A339448 a(4) = ( 7 - 1) mod 3 = 0,
%e A339448 a(5) = (11 - 0) mod 3 = 2.
%t A339448 a[0]=0; a[n_]:=Mod[Prime[n]-a[n-1],3]; Table[a[n],{n,0,85}] (* _Stefano Spezia_, Dec 05 2020 *)
%o A339448 (Ruby) require 'prime'
%o A339448 values = [0]
%o A339448 Prime.first(50).each do |prime|
%o A339448 values << (prime-values[-1]) % 3
%o A339448 end
%o A339448 p values
%Y A339448 Cf. A008347.
%K A339448 nonn
%O A339448 0,2
%A A339448 _Simon Strandgaard_, Dec 05 2020