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 A373904 #12 Jun 22 2024 14:12:23
%S A373904 1,1,2,8,30,98,303,937,2936,9260,29209,91999,289547,911255,2868341,
%T A373904 9029425,28424456,89478064,281667368,886657848,2791106585,8786123349,
%U A373904 27657838272,87064092870,274068969337,862741412709,2715822822365,8549136056237,26911817257385
%N A373904 a(n) = Sum_{k=0..floor(n/2)} binomial(n+4*k,n-2*k).
%H A373904 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (6,-14,20,-15,6,-1).
%F A373904 a(n) = 6*a(n-1) - 14*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6).
%F A373904 G.f.: 1/(1 - x - x^2/(1 - x)^5).
%o A373904 (PARI) a(n) = sum(k=0, n\2, binomial(n+4*k,n-2*k));
%Y A373904 Cf. A011782, A034943, A109961, A369840, A373908.
%Y A373904 Cf. A107025, A371125, A373905, A373906.
%K A373904 nonn,easy
%O A373904 0,3
%A A373904 _Seiichi Manyama_, Jun 22 2024