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 A017198 #20 Sep 08 2022 08:44:42
%S A017198 9,144,441,900,1521,2304,3249,4356,5625,7056,8649,10404,12321,14400,
%T A017198 16641,19044,21609,24336,27225,30276,33489,36864,40401,44100,47961,
%U A017198 51984,56169,60516,65025,69696
%N A017198 a(n) = (9*n + 3)^2.
%C A017198 a(n) = A000290(A017197(n)) = A156677(n+2) + A017305(n). - _Reinhard Zumkeller_, Jul 13 2010
%H A017198 Vincenzo Librandi, <a href="/A017198/b017198.txt">Table of n, a(n) for n = 0..10000</a>
%H A017198 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A017198 a(0)=9, a(1)=144, a(2)=441, a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - _Harvey P. Dale_, Dec 25 2015
%F A017198 G.f.: (-9 - 117*x - 36*x^2) / (x-1)^3. - _R. J. Mathar_, Jul 14 2016
%t A017198 (9*Range[0, 30] + 3)^2 (* or *) LinearRecurrence[{3,-3,1},{9,144,441},30] (* _Harvey P. Dale_, Dec 25 2015 *)
%o A017198 (Magma) [(9*n+3)^2: n in [0..35]]; // _Vincenzo Librandi_, Jul 23 2011
%o A017198 (PARI) a(n)=(9*n+3)^2 \\ _Charles R Greathouse IV_, Jun 17 2017
%K A017198 nonn,easy
%O A017198 0,1
%A A017198 _N. J. A. Sloane_