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 A266926 #71 Sep 08 2022 08:46:15
%S A266926 0,1,10,110,110110,110110110110,110110110110110110110110,
%T A266926 110110110110110110110110110110110110110110110110,
%U A266926 110110110110110110110110110110110110110110110110110110110110110110110110110110110110110110110110
%N A266926 a(0)=0, a(1)=1, a(2)=10; for n>2, a(n) = concat(a(1), ..., a(n-1)).
%C A266926 Decimal conversions: 0, 1, 2, 6, 54, 3510, 14380470, 241264265751990, 67909853583655146508751957430, ... . (See A267348.) - _Michael De Vlieger_, Jan 06 2016
%C A266926 After 10, a(n) is '110' repeated 2^(n-3) times. Therefore, for n>3, a(n) is the concatenation of a(n-1) with itself.
%C A266926 After 1, each term with the 0's omitted is a member of A136308.
%C A266926 The number of digits in a(n) is A098011(n+1).
%C A266926 The number of digits in a(n+2)/a(n+1) gives A103204 with 2 repeated.
%F A266926 a(n) = 110*(10^(3*2^(n-3))-1)/999 for n>2. - _Bruno Berselli_, Jan 29 2016
%e A266926 a(3) = concat(1, 10, 110) = 110110.
%e A266926 a(4) = concat(1, 10, 110, 110110) = 110110110110.
%t A266926 a = {0, 1}; Do[AppendTo[a, FromDigits@ Flatten@ Map[IntegerDigits@ # &, If[n < 2, Reverse@ a, a]]], {n, 8}]; a (* _Michael De Vlieger_, Jan 06 2016 *)
%o A266926 (Magma) [n le 2 select n*5^(n-1) else 110*(10^(3*2^(n-3))-1)/999: n in [0..8]]; // _Bruno Berselli_, Jan 29 2016
%Y A266926 Cf. A000079, A098011, A103204, A136308, A267348.
%K A266926 nonn,base,easy
%O A266926 0,3
%A A266926 _Giovanni Teofilatto_, Jan 06 2016
%E A266926 Definition by _Michael De Vlieger_, Jan 06 2016
%E A266926 Edited by Editors of the OEIS, Jan 29 2016