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 A177108 #20 Sep 08 2022 08:45:53
%S A177108 28,388,3988,39988,399988,3999988,39999988,399999988,3999999988,
%T A177108 39999999988,399999999988,3999999999988,39999999999988,
%U A177108 399999999999988,3999999999999988,39999999999999988,399999999999999988
%N A177108 a(n) = 4*(10^n-3).
%H A177108 Vincenzo Librandi, <a href="/A177108/b177108.txt">Table of n, a(n) for n = 1..200</a>
%H A177108 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A177108 G.f.: 4*x*(7+20*x) / ( (10*x-1)*(x-1) ). a(n)=4*A173833(n). - R. J. Mathar, Jan 06 2011
%F A177108 a(n) = a(n-1) +36*10^(n-1) = 10*a(n-1) +108 = 11*a(n-1) -10*a(n-2). - _Vincenzo Librandi_, Jul 15 2012
%t A177108 CoefficientList[Series[4*(7+20*x)/((10*x-1)*(x-1)),{x,0,40}],x] (* _Vincenzo Librandi_, Jul 15 2012 *)
%t A177108 4(10^Range[20]-3) (* or *) LinearRecurrence[{11,-10},{28,388},20] (* _Harvey P. Dale_, Sep 25 2012 *)
%o A177108 (Magma) [4*(10^n-3): n in [1..20]]; // _Vincenzo Librandi_, Jul 15 2012
%K A177108 nonn,easy
%O A177108 1,1
%A A177108 _Vincenzo Librandi_, Nov 15 2010