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 A154024 #35 Jan 03 2024 23:46:51
%S A154024 0,7,343,16800,822857,40303193,1974033600,96687343207,4735705783543,
%T A154024 231952896050400,11360956200686057,556454900937566393,
%U A154024 27254929189740067200,1334935075396325726407
%N A154024 a(n+2) = 49*a(n+1) - a(n), a(1)=0, a(2)=7.
%C A154024 If a(n)=x and a(n+1)=y, then (x^2+y^2)/(xy+1)=49.
%H A154024 Vincenzo Librandi, <a href="/A154024/b154024.txt">Table of n, a(n) for n = 1..600</a>
%H A154024 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (49,-1).
%F A154024 G.f.: 7*x^2/(1 -49*x +x^2). - _R. J. Mathar_, Jan 05 2011
%t A154024 LinearRecurrence[{49,-1},{0,7},30] (* _Vincenzo Librandi_, Feb 25 2012 *)
%t A154024 Rest@ CoefficientList[Series[7 x^2/(1 - 49 x + x^2), {x, 0, 14}], x] (* _Michael De Vlieger_, Sep 01 2016 *)
%o A154024 (PARI) concat(0,Vec(7/(1-49*x+x^2)+O(x^98))) \\ _Charles R Greathouse IV_, Dec 27 2011
%o A154024 (Magma) I:=[0, 7]; [n le 2 select I[n] else 49*Self(n-1)-Self(n-2): n in [1..50]]; // _Vincenzo Librandi_, Feb 25 2012
%Y A154024 Cf. A065100, A154021-A154027.
%K A154024 nonn,easy
%O A154024 1,2
%A A154024 _Vincenzo Librandi_, Jan 04 2009