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 A202020 #27 Mar 30 2017 08:40:19
%S A202020 1,4,16,68,305,1428,6914,34368,174438,900392,4712034,24944268,
%T A202020 133335497,718664500,3901458106,21313500576,117081025390,646328535800,
%U A202020 3583680016616,19949056745160,111447034042634
%N A202020 Number of 4-colored Motzkin paths of length n with no peaks at level 1.
%H A202020 Vincenzo Librandi, <a href="/A202020/b202020.txt">Table of n, a(n) for n = 0..200</a>
%F A202020 G.f.: (2*z^2-4*z+1 - sqrt(12*z^2-8*z+1))/(2*z^4-8*z^3+4 z^2).
%F A202020 Conjecture: 2(n+2)*a(n) -4*(5n+4)*a(n-1) +3*(19n-2)*a(n-2) +4*(11-14n)*a(n-4) +12*(n-1)*a(n-4)=0. - _R. J. Mathar_, Dec 18 2011
%F A202020 a(n) ~ 18*6^(n+3/2)/(49*sqrt(Pi)*n^(3/2)). - _Vaclav Kotesovec_, Oct 24 2012
%t A202020 CoefficientList[Series[(2*x^2-4*x+1-Sqrt[12*x^2-8*x+1])/(2*x^4-8*x^3+4*x^2), {x, 0, 20}], x] (* _Vaclav Kotesovec_, Oct 24 2012 *)
%o A202020 (PARI) z='z+O('z^50); Vec((2*z^2-4*z+1-sqrt(12*z^2-8*z+1))/(2*z^4-8*z^3+ 4*z^2)) \\ _G. C. Greubel_, Mar 29 2017
%Y A202020 Cf. A135334.
%K A202020 nonn
%O A202020 0,2
%A A202020 _José Luis Ramírez Ramírez_, Dec 08 2011