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 A100337 #3 Mar 30 2012 17:31:07
%S A100337 3,1,2,3,2,1,2,3,1,2,1,3,2,3,1,3,2,1,2,3,1,2,1,3,1,2,3,1,3,2,1,2,3,2,
%T A100337 1,3,2,3,1,2,1,3,1,2,3,2,1,3,2,3,1,3,2,1,2,3,1,2,1,3,1,2,3,1,3,2,1,2,
%U A100337 3,2,1,3,1,2,3,1,3,2,3,1,2,3,2,1,3,1,2,1,3,2,1,2,3,1,3,2,3,1,2,1,3,2,1,2,3
%N A100337 Arshon's sequence with a different start: start from 3 and replace the letters in odd positions using 1 -> 123, 2 -> 231, 3 -> 312 and the letters in even positions using 1 -> 321, 2-> 132, 3 -> 213.
%t A100337 f[n_List] := Block[{a = {}, l = Length[n], k = 1}, While[k < l + 1, If[EvenQ[k], Switch[ n[[k]], 1, AppendTo[a, 321], 2, AppendTo[a, 132], 3, AppendTo[a, 213]], Switch[ n[[k]], 1, AppendTo[a, 123], 2, AppendTo[a, 231], 3, AppendTo[a, 312]]]; k++ ]; Flatten[ IntegerDigits /@ a]]; Take[ Nest[f, {3}, 5], 105]
%Y A100337 Inspired by A099054. Cf. A100336.
%K A100337 nonn
%O A100337 1,1
%A A100337 _Robert G. Wilson v_, Nov 17 2004