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 A133558 #32 Jan 02 2024 08:55:10
%S A133558 1,2,11,29,128,389,1541,5042,18911,64289,234488,813089,2923481,
%T A133558 10241282,36552611,128724149,457697648,1616214989,5735493821,
%U A133558 20281428722,71900873111,254433731609,901541589608,3191445174089,11305319480561
%N A133558 a(n) = a(n-1) + 9*a(n-2) for n >= 2, a(0)=1, a(1)=2.
%H A133558 Muniru A Asiru, <a href="/A133558/b133558.txt">Table of n, a(n) for n = 0..400</a>
%H A133558 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1, 9).
%F A133558 G.f.: (1+x)/(1-x-9*x^2).
%F A133558 a(n) = Sum_{k=0..n+1} A122950(n+1,k)*8^(n+1-k). - _Philippe Deléham_, Jan 08 2008
%p A133558 a:=n->(<<0|1>,<9|1>>^n. <<1,2>>)[1,1]: seq(a(n),n=0..25); # _Muniru A Asiru_, Aug 04 2018
%t A133558 LinearRecurrence[{1,9},{1,2},30] (* or *) CoefficientList[Series[ (1+x)/(1-x-9x^2),{x,0,30}],x] (* _Harvey P. Dale_, Apr 21 2011 *)
%o A133558 (GAP) a:=[1,2]: for n in [3..510] do a[n]:=a[n-1]+9*a[n-2]; od; a; # _Muniru A Asiru_, Aug 04 2018
%K A133558 easy,nonn
%O A133558 0,2
%A A133558 _Philippe Deléham_, Jan 03 2008