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 A212987 #12 Feb 20 2024 03:36:36
%S A212987 1,1,3,5,8,10,16,18,25,29,37,41,52,56,68,74,87,93,109,115,132,140,158,
%T A212987 166,187,195,217,227,250,260,286,296,323,335,363,375,406,418,450,464,
%U A212987 497,511,547,561,598,614,652,668,709,725,767,785,828,846,892
%N A212987 Number of (w,x,y) with all terms in {0,...,n} and 3*w = 2*x+2*y.
%C A212987 For a guide to related sequences, see A212959.
%H A212987 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,1,-1,-2,0,1).
%F A212987 a(n) = 2*a(n-2)+a(n-3)-a(n-4)-2*a(n-5)+a(n-7).
%F A212987 G.f.: f(x)/g(x), where f(x) = 1 + x + x^2 + 2*x^3 + 2*x^4 and g(x) = (1 + x + x^2)((1+x)^2)((1-x)^3).
%t A212987 t = Compile[{{n, _Integer}}, Module[{s = 0}, (Do[If[3 w == 2 x + 2 y, s = s + 1], {w, 0, n}, {x, 0, n}, {y, 0, n}]; s)]];
%t A212987 m = Map[t[#] &, Range[0, 70]] (* A212987 *)
%Y A212987 Cf. A212959.
%K A212987 nonn,easy
%O A212987 0,3
%A A212987 _Clark Kimberling_, Jun 04 2012