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 A098706 #23 Jan 01 2021 11:31:02
%S A098706 0,2,10,290,9802,332930,11309770,384199202,13051463050,443365544450,
%T A098706 15061377048202,511643454094370,17380816062160330,590436102659356802,
%U A098706 20057446674355970890,681362750825443653410,23146276081390728245002,786292024016459316676610
%N A098706 a(n) = 2*A076218(n).
%H A098706 Colin Barker, <a href="/A098706/b098706.txt">Table of n, a(n) for n = 0..650</a>
%H A098706 Hacène Belbachir, Soumeya Merwa Tebtoub, and László Németh, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL23/Nemeth/nemeth7.html">Ellipse Chains and Associated Sequences</a>, J. Int. Seq., Vol. 23 (2020), Article 20.8.5.
%H A098706 Soumeya M. Tebtoub, Hacène Belbachir, and László Németh, <a href="https://hal.archives-ouvertes.fr/hal-02918958/document#page=18">Integer sequences and ellipse chains inside a hyperbola</a>, Proceedings of the 1st International Conference on Algebras, Graphs and Ordered Sets (ALGOS 2020), hal-02918958 [math.cs], 17-18.
%H A098706 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (35,-35,1).
%F A098706 a(0)=0, a(1)=2, and a(n) = 2*A001653(n-2) * A001653(n-1) for n>=2.
%F A098706 For n>1, a(n) = A002315(n-2)*A002315(n-1) + 3.
%F A098706 For n>0, a(n) = (A001542(n-1)-1)^2 + (A001542(n-1)-1)^2.
%F A098706 From _Colin Barker_, Mar 02 2016: (Start)
%F A098706 a(n) = (6+(17+12*sqrt(2))^(1-n)+(17-12*sqrt(2))*(17+12*sqrt(2))^n)/4 for n>0.
%F A098706 a(n) = 35*a(n-1)-35*a(n-2)+a(n-3) for n>3.
%F A098706 G.f.: 2*x*(1-30*x+5*x^2) / ((1-x)*(1-34*x+x^2)).
%F A098706 (End)
%e A098706 a(3) = 2*5*29 = 2*145.
%t A098706 LinearRecurrence[{35, -35, 1}, {0, 2, 10, 290}, 18] (* or *)
%t A098706 CoefficientList[Series[2 x (1 - 30 x + 5 x^2)/((1 - x) (1 - 34 x + x^2)), {x, 0, 17}], x] (* _Michael De Vlieger_, Nov 02 2020 *)
%o A098706 (PARI) concat(0, Vec(2*x*(1-30*x+5*x^2)/((1-x)*(1-34*x+x^2)) + O(x^20))) \\ _Colin Barker_, Mar 02 2016
%K A098706 nonn,easy
%O A098706 0,2
%A A098706 _Charlie Marion_, Oct 28 2004
%E A098706 More terms from _Ray Chandler_, Nov 10 2004