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 A165247 #24 Jun 18 2025 00:59:07
%S A165247 9,19,119,1119,11119,111119,1111119,11111119,111111119,1111111119,
%T A165247 11111111119,111111111119,1111111111119,11111111111119,
%U A165247 111111111111119,1111111111111119,11111111111111119,111111111111111119,1111111111111111119,11111111111111111119,111111111111111111119
%N A165247 a(n) = (10^n + 71)/9.
%C A165247 Also n - 1 ones followed by a nine.
%H A165247 Vincenzo Librandi, <a href="/A165247/b165247.txt">Table of n, a(n) for n = 1..100</a>
%H A165247 Markus Tervooren, <a href="https://factordb.com/index.php?query=%2810%5Ex%2B71%29%2F9">Factorizations of (1)w9</a>.
%H A165247 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A165247 G.f.: x*(9 - 80*x)/((1 - x)*(1 - 10*x)). - _Vincenzo Librandi_, Apr 26 2014
%F A165247 From _Elmo R. Oliveira_, Jun 17 2025: (Start)
%F A165247 E.g.f.: -8 + exp(x)*(71 + exp(9*x))/9.
%F A165247 a(n) = 11*a(n-1) - 10*a(n-2) for n >= 3. (End)
%t A165247 Table[FromDigits[PadLeft[{9}, n, 1]], {n, 20}] (* _Harvey P. Dale_, Apr 25 2014 *)
%t A165247 CoefficientList[Series[(9 - 80 x)/((1 - x) (1 - 10 x)), {x, 0, 30}], x] (* _Vincenzo Librandi_, Apr 26 2014 *)
%t A165247 (10^Range[20] + 71)/9 (* _Alonso del Arte_, Apr 18 2015 *)
%Y A165247 Cf. A093400, A104482.
%K A165247 easy,nonn
%O A165247 1,1
%A A165247 _Ivan Panchenko_, Sep 10 2009