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 A293156 #21 Sep 25 2018 17:40:18
%S A293156 15,36,99,292,876,2628,7884,23652,70956,212868,638604,1915812,5747436,
%T A293156 17242308,51726924,155180772,465542316,1396626948,4189880844,
%U A293156 12569642532,37708927596,113126782788,339380348364,1018141045092,3054423135276,9163269405828,27489808217484
%N A293156 Number of linear chord diagrams with n+2 chords such that every chord has length at least n.
%H A293156 Harvey P. Dale, <a href="/A293156/b293156.txt">Table of n, a(n) for n = 1..1000</a>
%H A293156 Everett Sullivan, <a href="https://arxiv.org/abs/1611.02771">Linear chord diagrams with long chords</a>, arXiv preprint arXiv:1611.02771 [math.CO], 2016.
%H A293156 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (3).
%F A293156 G.f.: (5*x^3+9*x^2+9*x-15)*x/(3*x-1). - _Alois P. Heinz_, Oct 17 2017
%F A293156 From _Colin Barker_, Oct 18 2017: (Start)
%F A293156 a(n) = 292*3^(n-4) for n>3.
%F A293156 a(n) = 3*a(n-1) for n>4.
%F A293156 (End)
%t A293156 Join[{15,36,99},NestList[3#&,292,30]] (* _Harvey P. Dale_, Sep 25 2018 *)
%o A293156 (PARI) Vec(x*(15 - 9*x - 9*x^2 - 5*x^3) / (1 - 3*x) + O(x^30)) \\ _Colin Barker_, Oct 18 2017
%Y A293156 A diagonal of A293157.
%K A293156 nonn,easy
%O A293156 1,1
%A A293156 _N. J. A. Sloane_, Oct 10 2017
%E A293156 More terms from _Alois P. Heinz_, Oct 17 2017