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 A167678 #6 Mar 31 2017 20:36:25
%S A167678 1,1,2,2,1,2,1,2,1,1,11,11,12,12,11,12,11,12,11,11,21,21,22,22,21,22,
%T A167678 21,22,21,21,21,21,22,22,21,22,21,22,21,21,11,11,12,12,11,12,11,12,11,
%U A167678 11,21,21,22,22,21,22,21,22,21,21,11,11,12,12,11,12,11,12,11,11,21,21,22
%N A167678 Replace prime digits with 2 and nonprime digits with 1.
%t A167678 Table[FromDigits[If[PrimeQ[ # ],2,1]&/@IntegerDigits[n]],{n,0,200}]
%Y A167678 Cf. A065031, A167677, A167679.
%K A167678 base,nonn
%O A167678 0,3
%A A167678 _Zak Seidov_, Nov 09 2009