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 A178511 #25 Dec 18 2023 12:16:00
%S A178511 1,81,8461,839241,84054421,8402966001,840343645981,84033470726361,
%T A178511 8403364056199141,840336082932216321,84033614424287889901,
%U A178511 8403361325938530091881,840336134807167928254261,84033613438663809363169041,8403361344665387622099788221
%N A178511 a(n) = (1/119)*(100^n -(-19)^n).
%C A178511 Numerators in alternating Sum_{n>=0} 19^n/100^(n+1).
%C A178511 Related to decimal expansion of fraction of 1/119 and Pell numbers. [In which way? - _Joerg Arndt_, May 14 2011]
%H A178511 Vincenzo Librandi, <a href="/A178511/b178511.txt">Table of n, a(n) for n = 1..150</a>
%H A178511 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (81,1900).
%F A178511 a(n+1) = a(n)*100 +- 19^n with a(0)=0 and a(1)= 1.
%F A178511 From _Colin Barker_, Oct 02 2015: (Start)
%F A178511 a(n) = 81*a(n-1) + 1900*a(n-2) for n > 2.
%F A178511 G.f.: -x / ((19*x+1)*(100*x-1)).
%F A178511 (End)
%t A178511 LinearRecurrence[{81,1900},{1,81},20] (* _Harvey P. Dale_, Nov 12 2022 *)
%o A178511 (Magma) [(1/119)*(100^n -(-19)^n): n in [1..20]]; // _Vincenzo Librandi_, May 17 2011
%o A178511 (PARI) Vec(-x/((19*x+1)*(100*x-1)) + O(x^20)) \\ _Colin Barker_, Oct 02 2015
%Y A178511 Cf. A000129, A021083, A038207, A178510.
%K A178511 nonn,frac,easy
%O A178511 1,2
%A A178511 _Mark Dols_, May 29 2010