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 A211621 #11 Dec 05 2017 06:08:25
%S A211621 0,3,29,103,247,484,843,1342,2008,2866,3938,5247,6822,8681,10851,
%T A211621 13357,16221,19466,23121,27204,31742,36760,42280,48325,54924,62095,
%U A211621 69865,78259,87299,97008,107415,118538,130404,143038,156462,170699,185778,201717,218543
%N A211621 Number of ordered triples (w,x,y) with all terms in {-n,...-1,1,...,n} and w+2x+3y>0.
%C A211621 For a guide to related sequences, see A211422.
%H A211621 Colin Barker, <a href="/A211621/b211621.txt">Table of n, a(n) for n = 0..1000</a>
%H A211621 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-1,-1,0,2,-1).
%F A211621 a(n) = 2*a(n-1) - a(n-3) - a(n-4) + 2*a(n-6) - a(n-7) for n>6.
%F A211621 G.f.: x*(3 + 23*x + 45*x^2 + 44*x^3 + 22*x^4 + 7*x^5) / ((1 - x)^4*(1 + x)*(1 + x + x^2)). - _Colin Barker_, Dec 05 2017
%t A211621 t = Compile[{{u, _Integer}}, Module[{s = 0}, (Do[If[w + 2 x + 3 y > 0, s = s + 1], {w, #}, {x, #}, {y, #}] &[Flatten[{Reverse[-#], #} &[Range[1, u]]]]; s)]];
%t A211621 Map[t[#] &, Range[0, 70]] (* A211621 *)
%t A211621 FindLinearRecurrence[%]
%t A211621 (* _Peter J. C. Moses_, Apr 13 2012 *)
%t A211621 LinearRecurrence[{2, 0, -1, -1, 0, 2, -1},{0, 3, 29, 103, 247, 484, 843},36] (* _Ray Chandler_, Aug 02 2015 *)
%o A211621 (PARI) concat(0, Vec(x*(3 + 23*x + 45*x^2 + 44*x^3 + 22*x^4 + 7*x^5) / ((1 - x)^4*(1 + x)*(1 + x + x^2)) + O(x^40))) \\ _Colin Barker_, Dec 05 2017
%Y A211621 Cf. A211422.
%K A211621 nonn,easy
%O A211621 0,2
%A A211621 _Clark Kimberling_, Apr 16 2012