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 A281366 #14 Jan 30 2017 03:50:20
%S A281366 1,2,3,10,11,20,21,100,110,200,210,1000,1100,2000,2100,10000,11000,
%T A281366 20000,21000,100000,110000,200000,210000,1000000,1100000,2000000,
%U A281366 2100000,10000000,11000000,20000000,21000000,100000000,110000000,200000000,210000000
%N A281366 Lexicographically least strictly increasing sequence such that, for any n>0, Sum_{k=1..n} a(k) can be computed without carries in base 9 (the numbers are written in base 9).
%C A281366 Base 9 analog of A278742.
%H A281366 Colin Barker, <a href="/A281366/b281366.txt">Table of n, a(n) for n = 1..1000</a>
%H A281366 N. J. A. Sloane, <a href="/A280731/a280731.jpg">Illustration of initial terms</a>
%H A281366 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,10).
%F A281366 From _Colin Barker_, Jan 29 2017: (Start)
%F A281366 G.f.: x*(1 + 2*x + 3*x^2 + 10*x^3 + x^4 - 9*x^6)/(1 - 10*x^4).
%F A281366 a(n) = 10*a(n-4) for n>7. (End)
%o A281366 (PARI) Vec(x*(1 + 2*x + 3*x^2 + 10*x^3 + x^4 - 9*x^6) / (1 - 10*x^4) + O(x^60)) \\ _Colin Barker_, Jan 29 2017
%Y A281366 Cf. A278742, A278743, A280051, A280052.
%Y A281366 See A280731 for these numbers written in base 10.
%K A281366 nonn,base,easy
%O A281366 1,2
%A A281366 _N. J. A. Sloane_, Jan 28 2017
%E A281366 More terms from _Colin Barker_, Jan 29 2017