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 A190869 #38 Sep 08 2022 08:45:57
%S A190869 0,1,10,98,960,9404,92120,902392,8839680,86592016,848240800,
%T A190869 8309223968,81395758080,797339132864,7810599812480,76511319859072,
%U A190869 749491998965760,7341897349939456,71919989501463040,704516100314751488,6901321024144588800,67604178040816385024
%N A190869 a(n) = 10*a(n-1) - 2*a(n-2), a(0)=0, a(1)=1.
%C A190869 a(n+1) equals the number of words of length n over {0,1,2,3,4,5,6,7,8,9} avoiding 01 and 02. - _Milan Janjic_, Dec 17 2015
%H A190869 Robert Israel, <a href="/A190869/b190869.txt">Table of n, a(n) for n = 0..990</a>
%H A190869 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (10, -2).
%F A190869 a(n) = ((5+sqrt(23))^n-(5-sqrt(23))^n)/(2*sqrt(23)).
%F A190869 G.f.: x/(1-10*x+2*x^2). - _Robert Israel_, Dec 17 2015
%p A190869 f:= gfun:-rectoproc({a(n) = 10*a(n-1) - 2*a(n-2), a(0)=0, a(1)=1},a(n),remember):
%p A190869 map(f, [$0..50]); # _Robert Israel_, Dec 17 2015
%t A190869 LinearRecurrence[{10, -2}, {0, 1}, 50] (* _T. D. Noe_, May 23 2011 *)
%o A190869 (Magma) I:=[0,1]; [n le 2 select I[n] else 10*Self(n-1)-2*Self(n-2): n in [1..30]]; // _Vincenzo Librandi_, Dec 17 2015
%o A190869 (PARI) concat(0, Vec(x/(1-10*x+2*x^2) + O(x^100))) \\ _Altug Alkan_, Dec 17 2015
%K A190869 nonn,easy
%O A190869 0,3
%A A190869 _Rolf Pleisch_, May 22 2011
%E A190869 Corrected and extended by _T. D. Noe_, May 23 2011