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 A154518 #29 Sep 08 2022 08:45:40
%S A154518 204,420,636,852,1068,1284,1500,1716,1932,2148,2364,2580,2796,3012,
%T A154518 3228,3444,3660,3876,4092,4308,4524,4740,4956,5172,5388,5604,5820,
%U A154518 6036,6252,6468,6684,6900,7116,7332,7548,7764,7980,8196,8412,8628
%N A154518 a(n) = 216*n - 12.
%C A154518 The identity (648*n^2 - 72*n + 1)^2 - (9*n^2 - n)*(216*n - 12)^2 = 1 can be written as A154514(n)^2 - A154516(n)*a(n)^2 = 1 (see also the second comment at A154514). - _Vincenzo Librandi_, Jan 30 2012
%H A154518 Vincenzo Librandi, <a href="/A154518/b154518.txt">Table of n, a(n) for n = 1..10000</a>
%H A154518 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A154518 From _R. J. Mathar_, Jul 29 2009: (Start)
%F A154518 a(n) = 12*(18n-1).
%F A154518 O.g.f.: 12*x*(17+x)/(x-1)^2. (End)
%F A154518 a(n) = 2*a(n-1) - a(n-2).
%t A154518 216Range[40]-12 (* _Harvey P. Dale_, Feb 01 2011 *)
%t A154518 LinearRecurrence[{2, -1}, {204, 420}, 50] (* _Vincenzo Librandi_, Jan 30 2012 *)
%o A154518 (PARI) a(n)=216*n-12 \\ _Charles R Greathouse IV_, Dec 27 2011
%o A154518 (Magma) I:=[204, 420]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]]; // _Vincenzo Librandi_, Jan 30 2012
%Y A154518 Cf. A154514, A154516.
%K A154518 nonn,easy
%O A154518 1,1
%A A154518 _Vincenzo Librandi_, Jan 11 2009