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 A081549 #14 Aug 17 2015 16:32:47
%S A081549 1,2,3,4,5,6,7,8,9,12,34,56,78,91,234,567,891,2345,6789,12345,67891,
%T A081549 234567,891234,5678912,34567891,234567891,2345678912,3456789123,
%U A081549 4567891234,5678912345,6789123456,7891234567,8912345678,9123456789
%N A081549 a(1) = 1; for n > 1, a(n) > a(n-1) is the smallest number such that the concatenation a(1)a(2)a(3)... forms a cyclic concatenation of 123456789 (of nonzero digits).
%H A081549 Ivan Neretin, <a href="/A081549/b081549.txt">Table of n, a(n) for n = 1..500</a>
%t A081549 a = {1}; c = 0; Do[c = 10 c + Mod[n, 9] + 1; If[c > a[[-1]], AppendTo[a, c]; c = 0], {n, 170}]; a (* _Ivan Neretin_, Aug 14 2015 *)
%Y A081549 Cf. A165307 (non-monotonic version), A007923 (version with strictly increasing length).
%K A081549 base,easy,nonn
%O A081549 1,2
%A A081549 _Amarnath Murthy_, Apr 01 2003
%E A081549 Corrected and extended by _Sean A. Irvine_, Apr 18 2010