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 A212985 #21 Apr 19 2023 02:33:51
%S A212985 1,2,3,7,9,11,18,21,24,34,38,42,55,60,65,81,87,93,112,119,126,148,156,
%T A212985 164,189,198,207,235,245,255,286,297,308,342,354,366,403,416,429,469,
%U A212985 483,497,540,555,570,616,632,648,697,714,731,783,801,819,874
%N A212985 Number of (w,x,y) with all terms in {0,...,n} and 3w = 3x + y.
%C A212985 For a guide to related sequences, see A212959.
%H A212985 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,2,-2,0,-1,1).
%F A212985 a(n) = a(n-1) + 2*a(n-3) - 2*a(n-4) - a(n-6) + a(n-7).
%F A212985 G.f.: f(x)/g(x), where f(x) = 1 + x + x^2 + 2*x^3 and g(x) = ((1+x+x^2)^2)*((1-x)^3).
%t A212985 t = Compile[{{n, _Integer}}, Module[{s = 0},
%t A212985 (Do[If[3 w == 3 x + y, s = s + 1],
%t A212985 {w, 0, n}, {x, 0, n}, {y, 0, n}]; s)]];
%t A212985 m = Map[t[#] &, Range[0, 70]] (* A212985 *)
%Y A212985 Cf. A212959.
%K A212985 nonn,easy
%O A212985 0,2
%A A212985 _Clark Kimberling_, Jun 04 2012