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 A212685 #11 Aug 01 2015 10:26:05
%S A212685 0,0,2,7,18,36,64,103,156,224,310,415,542,692,868,1071,1304,1568,1866,
%T A212685 2199,2570,2980,3432,3927,4468,5056,5694,6383,7126,7924,8780,9695,
%U A212685 10672,11712,12818,13991,15234,16548,17936,19399,20940,22560
%N A212685 Number of (w,x,y,z) with all terms in {1,...,n} and |w-x|=w+|y-z|.
%C A212685 For a guide to related sequences, see A211795.
%H A212685 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (3, -2, -2, 3, -1).
%F A212685 a(n)=3*a(n-1)-2*a(n-2)-2*a(n-3)+3*a(n-4)-a(n-5).
%F A212685 G.f.: (2*x^2 + x^3 + x^4)/(1 - 3*x + 2*x^2 + 2*x^3 - 3*x^4 + x^5).
%F A212685 a(n)=(-3+3*(-1)^n+4*n-6*n^2+8*n^3)/24. [_Colin Barker_, Jun 10 2012]
%t A212685 t = Compile[{{n, _Integer}}, Module[{s = 0},
%t A212685 (Do[If[Abs[w - x] == w + Abs[y - z], s = s + 1],
%t A212685 {w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
%t A212685 Map[t[#] &, Range[0, 40]] (* A212685 *)
%t A212685 LinearRecurrence[{3, -2, -2, 3, -1}, {0, 0, 2, 7, 18}, 40]
%Y A212685 Cf. A211795.
%K A212685 nonn,easy
%O A212685 0,3
%A A212685 _Clark Kimberling_, May 24 2012