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 A177109 #18 Jul 26 2024 13:14:13
%S A177109 20,380,3980,39980,399980,3999980,39999980,399999980,3999999980,
%T A177109 39999999980,399999999980,3999999999980,39999999999980,
%U A177109 399999999999980,3999999999999980,39999999999999980,399999999999999980
%N A177109 a(n) = 4*(10^n-5).
%C A177109 Is this 20*A067272(n)?
%H A177109 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A177109 G.f.: 20*x*(1+8*x) / ( (10*x-1)*(x-1) ). - _R. J. Mathar_, Jan 06 2011
%F A177109 a(n) = 11*a(n-1) - 10*a(n-2). - _Wesley Ivan Hurt_, Mar 17 2023
%p A177109 A177109:=n->4*(10^n-5): seq(A177109(n), n=1..30); # _Wesley Ivan Hurt_, Feb 16 2017
%t A177109 4(10^Range[20]-5) (* or *) LinearRecurrence[{11,-10},{20,380},20] (* _Harvey P. Dale_, Jul 26 2024 *)
%Y A177109 Cf. A067272.
%K A177109 nonn,easy
%O A177109 1,1
%A A177109 _Vincenzo Librandi_, Nov 15 2010