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 A144900 #16 Jul 27 2022 10:37:13
%S A144900 0,1,7,28,85,218,498,1045,2055,3840,6887,11945,20153,33228,53741,
%T A144900 85522,134254,208344,320200,488103,738951,1112281,1666164,2485845,
%U A144900 3696406,5481325,8109676,11975993,17658694,26005706,38259955,56243281,82625979,121321831,178067054
%N A144900 Expansion of x/((1-x-x^3)*(1-x)^6).
%H A144900 Vincenzo Librandi, <a href="/A144900/b144900.txt">Table of n, a(n) for n = 0..1000</a>
%H A144900 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (7,-21,36,-41,36,-27,16,-6,1).
%F A144900 G.f.: x/((1-x-x^3)*(1-x)^6).
%F A144900 From _G. C. Greubel_, Jul 27 2022: (Start)
%F A144900 a(n) = Sum_{j=0..floor((n+5)/3)} binomial(n-2*j+5, j+6).
%F A144900 a(n) = A099567(n+5, 6). (End)
%p A144900 a:= n-> (Matrix(9, (i, j)-> if i=j-1 then 1 elif j=1 then [7, -21, 36, -41, 36, -27, 16, -6, 1][i] else 0 fi)^n)[1, 2]: seq(a(n), n=0..40);
%t A144900 CoefficientList[Series[x/((1-x-x^3)(1-x)^6), {x,0,40}], x] (* _Vincenzo Librandi_, Jun 06 2013 *)
%t A144900 LinearRecurrence[{7,-21,36,-41,36,-27,16,-6,1},{0,1,7,28,85,218,498,1045,2055},40] (* _Harvey P. Dale_, Mar 02 2016 *)
%o A144900 (Magma)
%o A144900 A144900:= func< n | n eq 0 select 0 else (&+[Binomial(n-2*j+5, j+6): j in [0..Floor((n+5)/3)]]) >;
%o A144900 [A144900(n): n in [0..40]]; // _G. C. Greubel_, Jul 27 2022
%o A144900 (SageMath)
%o A144900 def A144900(n): return sum(binomial(n-2*j+5, j+6) for j in (0..((n+5)//3)))
%o A144900 [A144900(n) for n in (0..40)] # _G. C. Greubel_, Jul 27 2022
%Y A144900 7th column of A144903.
%Y A144900 Cf. A099567.
%K A144900 nonn,easy
%O A144900 0,3
%A A144900 _Alois P. Heinz_, Sep 24 2008