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 A173776 #20 Sep 08 2022 08:45:50
%S A173776 5,9,49,449,4449,44449,444449,4444449,44444449,444444449,4444444449,
%T A173776 44444444449,444444444449,4444444444449,44444444444449,
%U A173776 444444444444449,4444444444444449,44444444444444449,444444444444444449
%N A173776 a(n) = (4*10^n + 41)/9.
%H A173776 Vincenzo Librandi, <a href="/A173776/b173776.txt">Table of n, a(n) for n = 0..100</a>
%H A173776 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10).
%F A173776 a(n) = 10*a(n-1) - 41 with n>0, a(0)=5.
%F A173776 G.f.: (5 - 46*x)/((1-x)*(1-10*x)). - _Vincenzo Librandi_, Jul 05 2012
%F A173776 a(n) = 11*a(n-1) -10*a(n-2). - _Vincenzo Librandi_, Jul 05 2012
%F A173776 E.g.f.: (1/9)*(41*exp(x) + 4*exp(10*x)). - _G. C. Greubel_, Jul 06 2021
%t A173776 Join[{5}, FromDigits/@Table[PadLeft[{9}, n, 4], {n,20}]] (* or *) Join[{5}, NestList[10#-41&, 9, 20]] (* _Harvey P. Dale_, Feb 17 2012 *)
%t A173776 CoefficientList[Series[(5-46*x)/((1-x)*(1-10*x)),{x,0,30}],x] (* _Vincenzo Librandi_, Jul 05 2012 *)
%o A173776 (Magma) [(4*10^n+41)/9: n in [0..20]]; // _Vincenzo Librandi_, Jul 05 2012
%o A173776 (Sage) [(4*10^n + 41)/9 for n in (0..30)] # _G. C. Greubel_, Jul 06 2021
%Y A173776 Cf. A093402.
%K A173776 nonn,easy
%O A173776 0,1
%A A173776 _Vincenzo Librandi_, Feb 24 2010