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 A212989 #13 Sep 20 2023 11:52:27
%S A212989 1,2,3,4,9,11,13,15,24,27,30,33,46,50,54,58,75,80,85,90,111,117,123,
%T A212989 129,154,161,168,175,204,212,220,228,261,270,279,288,325,335,345,355,
%U A212989 396,407,418,429,474,486,498,510,559,572,585,598,651,665,679,693
%N A212989 Number of (w,x,y) with all terms in {0,...,n} and 4*w = 4*x+y.
%C A212989 For a guide to related sequences, see A212959.
%H A212989 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, 0, 2, -2, 0, 0, -1, 1).
%F A212989 a(n) = a(n-1)+2*a(n-3)-2*a(n-4)-a(n-7)+a(n-8).
%F A212989 G.f.: f(x)/g(x), where f(x) = 1 + x + x^2 + x^3 + 3*x^4 and g(x) = ((1 + x + x^2 + x^3)^2)(1-x)^3.
%t A212989 t = Compile[{{n, _Integer}}, Module[{s = 0},
%t A212989 (Do[If[4 w == 4 x + y, s = s + 1],
%t A212989 {w, 0, n}, {x, 0, n}, {y, 0, n}]; s)]];
%t A212989 m = Map[t[#] &, Range[0, 70]] (* A212989 *)
%t A212989 LinearRecurrence[{1,0,0,2,-2,0,0,-1,1},{1,2,3,4,9,11,13,15,24},60] (* _Harvey P. Dale_, Sep 20 2023 *)
%Y A212989 Cf. A212959.
%K A212989 nonn,easy
%O A212989 0,2
%A A212989 _Clark Kimberling_, Jun 04 2012