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 A173810 #31 Oct 12 2024 03:17:27
%S A173810 1,81,881,8881,88881,888881,8888881,88888881,888888881,8888888881,
%T A173810 88888888881,888888888881,8888888888881,88888888888881,
%U A173810 888888888888881,8888888888888881,88888888888888881,888888888888888881,8888888888888888881,88888888888888888881,888888888888888888881
%N A173810 a(n) = (8*10^n - 71)/9 for n > 0.
%H A173810 Vincenzo Librandi, <a href="/A173810/b173810.txt">Table of n, a(n) for n = 1..100</a>
%H A173810 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A173810 a(n) = 10*a(n-1) + 71 for n > 0, a(0) = -7.
%F A173810 From _Vincenzo Librandi_, Jul 05 2012: (Start)
%F A173810 G.f.: x*(1+70*x)/((1-x)*(1-10*x)).
%F A173810 a(n) = 11*a(n-1) - 10*a(n-2). (End)
%F A173810 E.g.f.: exp(x)*(8*exp(9*x) - 71)/9. - _Elmo R. Oliveira_, Sep 09 2024
%p A173810 A173810:=n->(8*10^n-71)/9; seq(A173810(k), k=1..50); # _Wesley Ivan Hurt_, Nov 05 2013
%t A173810 CoefficientList[Series[x(1+70*x)/((1-x)*(1-10*x)),{x,0,30}],x] (* _Vincenzo Librandi_, Jul 05 2012 *)
%t A173810 LinearRecurrence[{11,-10},{1,81},30] (* _Harvey P. Dale_, Feb 20 2016 *)
%o A173810 (Magma) [(8*10^n-71)/9: n in [1..20]]; // _Vincenzo Librandi_, Jul 05 2012
%Y A173810 Cf. A092675.
%K A173810 nonn,easy
%O A173810 1,2
%A A173810 _Vincenzo Librandi_, Feb 25 2010