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 A133673 #22 Apr 06 2021 04:40:36
%S A133673 7,18,40,83,163,311,579,1060,1914,3419,6053,10637,18575,32262,55772,
%T A133673 96019,164711,281635,480171,816536,1385262,2345083,3962185,6682393,
%U A133673 11251543,18916026,31756624,53243795,89160619,149135759,249187923,415946572,693648930
%N A133673 a(n) = n*L(n) + (n-1)*L(n-1) where L(n) is the Lucas number.
%C A133673 For n>2, two evens followed by four odds.
%H A133673 Harvey P. Dale, <a href="/A133673/b133673.txt">Table of n, a(n) for n = 2..1000</a>
%H A133673 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,1,-2,-1).
%F A133673 From _R. J. Mathar_, Jul 08 2009, Jul 13 2009: (Start)
%F A133673 G.f.: -x^2*(-7-4*x+3*x^2+x^3)/(x^2+x-1)^2.
%F A133673 a(n) = 2*a(n-1)+a(n-2)-2*a(n-3)-a(n-4).
%F A133673 a(n) = A146005(n) + A146005(n-1). (End)
%e A133673 For n=2, a(2) = 7;
%e A133673 For n=21, a(21) = 816536.
%t A133673 Total/@Partition[Times@@@Table[{n,LucasL[n]},{n,30}],2,1] (* or *) LinearRecurrence[{2,1,-2,-1},{7,18,40,83},30](* _Harvey P. Dale_, Oct 21 2011 *)
%Y A133673 Cf. A000032, A136376, A146005.
%K A133673 nonn,easy
%O A133673 2,1
%A A133673 _Parthasarathy Nambi_, Dec 29 2007
%E A133673 Typo in A-numbers corrected by _R. J. Mathar_, Jul 13 2009
%E A133673 More terms from _Harvey P. Dale_, Oct 21 2011