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 A017018 #25 May 07 2024 06:31:54
%S A017018 9,100,289,576,961,1444,2025,2704,3481,4356,5329,6400,7569,8836,10201,
%T A017018 11664,13225,14884,16641,18496,20449,22500,24649,26896,29241,31684,
%U A017018 34225,36864,39601,42436,45369,48400
%N A017018 a(n) = (7*n + 3)^2.
%H A017018 Vincenzo Librandi, <a href="/A017018/b017018.txt">Table of n, a(n) for n = 0..10000</a>
%H A017018 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A017018 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3); a(0)=9, a(1)=100, a(2)=289. - _Harvey P. Dale_, Jul 19 2014
%F A017018 G.f.: (9 + 73*x + 16*x^2)/(1-x)^3. - _Harvey P. Dale_, Jul 19 2014
%F A017018 E.g.f.: (9 + 91*x + 49*x^2)*exp(x). - _G. C. Greubel_, Oct 17 2023
%F A017018 Sum_{n>=0} 1/a(n) = psi'(3/7)/49 = 0.13147479209450263890925... - _R. J. Mathar_, May 07 2024
%t A017018 (7*Range[0,40]+3)^2 (* or *) LinearRecurrence[{3,-3,1},{9,100,289},40] (* _Harvey P. Dale_, Jul 19 2014 *)
%o A017018 (Magma) [(7*n+3)^2: n in [0..35]]; // _Vincenzo Librandi_, Jul 14 2011
%o A017018 (PARI) a(n)=(7*n+3)^2 \\ _Charles R Greathouse IV_, Jun 17 2017
%o A017018 (SageMath) [(7*n+3)^2 for n in range(40)] # _G. C. Greubel_, Oct 17 2023
%Y A017018 Cf. A017017.
%K A017018 nonn,easy
%O A017018 0,1
%A A017018 _N. J. A. Sloane_