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 A373653 #8 Jun 12 2024 17:21:58
%S A373653 1,1,1,4,7,16,34,71,153,322,686,1455,3088,6558,13917,29548,62721,
%T A373653 133146,282646,599998,1273690,2703794,5739647,12184181,25864698,
%U A373653 54905857,116554700,247423522,525233175,1114970351,2366870474,5024416818,10665883415,22641646338
%N A373653 a(n) = Sum_{k=0..floor(n/2)} binomial(3*n-5*k-1,k).
%H A373653 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (1,3,0,-3,0,1).
%F A373653 G.f.: 1 / (1 - x/(1 - x^2)^3).
%F A373653 a(n) = a(n-1) + 3*a(n-2) - 3*a(n-4) + a(n-6) for n > 6.
%o A373653 (PARI) a(n) = sum(k=0, n\2, binomial(3*n-5*k-1, k));
%Y A373653 Cf. A158943, A373638.
%K A373653 nonn,easy
%O A373653 0,4
%A A373653 _Seiichi Manyama_, Jun 12 2024