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 A173806 #19 Sep 09 2024 12:29:19
%S A173806 1,71,771,7771,77771,777771,7777771,77777771,777777771,7777777771,
%T A173806 77777777771,777777777771,7777777777771,77777777777771,
%U A173806 777777777777771,7777777777777771,77777777777777771,777777777777777771,7777777777777777771,77777777777777777771,777777777777777777771
%N A173806 a(n) = (7*10^n - 61)/9 for n > 0.
%H A173806 Vincenzo Librandi, <a href="/A173806/b173806.txt">Table of n, a(n) for n = 1..100</a>
%H A173806 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A173806 a(n) = 10*a(n-1) + 61 with n > 0, a(0)=-6.
%F A173806 From _Vincenzo Librandi_, Jul 05 2012: (Start)
%F A173806 G.f.: x*(1+60*x)/((1-x)*(1-10*x)).
%F A173806 a(n) = 11*a(n-1) - 10*a(n-2) for n > 2. (End)
%F A173806 E.g.f.: 6 + exp(x)*(7*exp(9*x) - 61)/9. - _Elmo R. Oliveira_, Sep 09 2024
%t A173806 CoefficientList[Series[(1+60*x)/((1-x)*(1-10*x)),{x,0,30}],x] (* _Vincenzo Librandi_, Jul 05 2012 *)
%o A173806 (Magma)[(7*10^n-61)/9: n in [1..20]]; // _Vincenzo Librandi_, Jul 05 2012
%Y A173806 Cf. A093176.
%K A173806 nonn,easy
%O A173806 1,2
%A A173806 _Vincenzo Librandi_, Feb 25 2010