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 A271895 #9 Apr 16 2016 13:16:22
%S A271895 1,2,6,14,40,100,276,712,1928,5048,13536,35696,95248,252064,670944,
%T A271895 1778656,4728704,12546368,33335616,88484480,235033216,623990656,
%U A271895 1657207296,4400177920,11685241088,31027950080,82395796992,218791947776,580999383040,1542791775232
%N A271895 Expansion of (1-2*x^2) / ( 1-2*x-4*x^2+6*x^3 ).
%C A271895 Sum of all third elements at level n of the TRIP-Stern sequence corresponding to the permutation triple (e,13,23)
%H A271895 Ilya Amburg, Krishna Dasaratha, Laure Flapan, Thomas Garrity, Chansoo Lee, Cornelia Mihaila, Nicholas Neumann-Chun, Sarah Peluse, Matthew Stoffregen, <a href="http://arxiv.org/abs/1509.05239">Stern Sequences for a Family of Multidimensional Continued Fractions: TRIP-Stern Sequences</a>, arXiv:1509.05239 [math.CO], 2015, Section 7.2.1
%H A271895 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,4,-6).
%F A271895 a(n) >= 2^n.
%o A271895 (PARI) x='x+O('x^99); Vec((1-2*x^2)/(1-2*x-4*x^2+6*x^3)) \\ _Altug Alkan_, Apr 16 2016
%Y A271895 Cf. A271486 (maximum at level n).
%K A271895 nonn,easy
%O A271895 0,2
%A A271895 _R. J. Mathar_, Apr 16 2016