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 A325494 #8 May 06 2019 08:48:29
%S A325494 1,2,3,1,2,1,2,1,2,2,1,1,2,3,1,2,3,1,2,1,1,2,2,3,1,2,1,2,1,2,3,1,2,1,
%T A325494 2,1,2,3,1,2,2,2,2,3,1,2,1,2,1,2,2,1,1,2,3,1,2,3,1,2,1,2,1,2,3,1,2,3,
%U A325494 1,2,2,1,1,2,1,2,1,2,3,1,2,1,1,2,2,3
%N A325494 Difference sequence of A325419.
%C A325494 See A325417 for a guide to related sequences. Conjecture: every term is in {1,2,3}.
%H A325494 Clark Kimberling, <a href="/A325494/b325494.txt">Table of n, a(n) for n = 1..10000</a>
%e A325494 A325419 is given by A(n) = least number not 3*A(m) or 2*A(m)+1 for any m < n, so that A = (1,2,4,7,8,10,11,...), with differences (1,2,3,1,2,1,...).
%t A325494 a = {1}; Do[AppendTo[a, NestWhile[# + 1 &, Last[a] + 1,
%t A325494 Apply[Or, Map[MemberQ[a, #] &, Select[Flatten[{#/3, (# - 1)/2}],
%t A325494 IntegerQ]]] &]], {2000}]; a ; (* A325419 *)
%t A325494 c = Complement[Range[Last[a]], a] ; (* A325420 *)
%t A325494 Differences[a] (* A325494 *)
%t A325494 Differences[c] (* A325495 *)
%t A325494 (* _Peter J. C. Moses_, Apr 23 2019 *)
%Y A325494 Cf. A325417, A325495.
%K A325494 nonn,easy
%O A325494 1,2
%A A325494 _Clark Kimberling_, May 05 2019