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 A036542 #11 Jul 21 2024 12:25:10
%S A036542 1,3,11,34,93,236,571,1338,3065,6904,15351,33782,73717,159732,344051,
%T A036542 737266,1572849,3342320,7077871,14942190,31457261,66060268,138412011,
%U A036542 289406954,603979753,1258291176,2617245671,5435817958,11274289125,23353884644,48318382051
%N A036542 a(n) = T(n, n), array T given by A047858.
%H A036542 Colin Barker, <a href="/A036542/b036542.txt">Table of n, a(n) for n = 0..1000</a>
%H A036542 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6,-13,12,-4).
%F A036542 a(n) = 3*n * 2^(n-1) - n + 1.
%F A036542 From _Colin Barker_, Feb 20 2016: (Start)
%F A036542 a(n) = 6*a(n-1)-13*a(n-2)+12*a(n-3)-4*a(n-4) for n>3.
%F A036542 G.f.: (1-3*x+6*x^2-5*x^3) / ((1-x)^2*(1-2*x)^2).
%F A036542 (End)
%t A036542 LinearRecurrence[{6,-13,12,-4},{1,3,11,34},40] (* _Harvey P. Dale_, Jul 21 2024 *)
%o A036542 (PARI) Vec((1-3*x+6*x^2-5*x^3)/((1-x)^2*(1-2*x)^2) + O(x^40)) \\ _Colin Barker_, Feb 20 2016
%K A036542 nonn,easy
%O A036542 0,2
%A A036542 _Clark Kimberling_