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 A173833 #27 May 07 2025 09:13:27
%S A173833 7,97,997,9997,99997,999997,9999997,99999997,999999997,9999999997,
%T A173833 99999999997,999999999997,9999999999997,99999999999997,
%U A173833 999999999999997,9999999999999997,99999999999999997,999999999999999997,9999999999999999997,99999999999999999997,999999999999999999997
%N A173833 a(n) = 10^n - 3.
%H A173833 Vincenzo Librandi, <a href="/A173833/b173833.txt">Table of n, a(n) for n = 1..100</a>
%H A173833 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A173833 a(n) = 10*a(n-1) + 27 with n > 1, a(1)=7.
%F A173833 G.f.: x*(20*x+7)/((x-1)*(10*x-1)). - _Colin Barker_, Jan 24 2013
%F A173833 E.g.f.: 2 - 3*exp(x) + exp(10*x). - _Stefano Spezia_, May 02 2025
%F A173833 From _Elmo R. Oliveira_, May 07 2025: (Start)
%F A173833 a(n) = 11*a(n-1) - 10*a(n-2) for n > 2.
%F A173833 a(n) = A086947(n)/3. (End)
%t A173833 LinearRecurrence[{11, -10}, {7, 97}, 20] (* _Vincenzo Librandi_, Feb 22 2012 *)
%o A173833 (PARI) a(n)=10^n-3 \\ _Charles R Greathouse IV_, Jan 11 2012
%Y A173833 Cf. A011557, A086947.
%K A173833 nonn,easy
%O A173833 1,1
%A A173833 _Vincenzo Librandi_, Feb 26 2010