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 A373655 #8 Jun 12 2024 17:22:17
%S A373655 1,1,1,1,4,7,10,19,37,64,110,201,364,641,1140,2050,3662,6516,11638,
%T A373655 20811,37140,66268,118356,211368,377308,673605,1202805,2147563,
%U A373655 3834121,6845572,12222605,21822509,38962178,69564612,124203381,221756004,395929588,706906325
%N A373655 a(n) = Sum_{k=0..floor(n/3)} binomial(3*n-8*k-1,k).
%H A373655 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,3,0,0,-3,0,0,1).
%F A373655 G.f.: 1 / (1 - x/(1 - x^3)^3).
%F A373655 a(n) = a(n-1) + 3*a(n-3) - 3*a(n-6) + a(n-9) for n > 9.
%o A373655 (PARI) a(n) = sum(k=0, n\3, binomial(3*n-8*k-1, k));
%Y A373655 Cf. A373640.
%K A373655 nonn,easy
%O A373655 0,5
%A A373655 _Seiichi Manyama_, Jun 12 2024