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 A376809 #14 Oct 05 2024 02:46:19
%S A376809 1,0,0,2,4,6,14,34,72,154,346,774,1714,3822,8574,19238,43204,97254,
%T A376809 219286,494962,1118502,2530522,5730762,12989634,29467718,66901378,
%U A376809 151996338,345556218,786092266,1789284762,4074927962,9284968682,21166439112,48273612954,110142596298
%N A376809 Expansion of 1/sqrt(1 - 4*x^3/(1 - x)^2).
%F A376809 a(n) = Sum_{k=0..floor(n/3)} binomial(2*k,k) * binomial(n-k-1,n-3*k).
%o A376809 (PARI) my(N=40, x='x+O('x^N)); Vec(1/sqrt(1-4*x^3/(1-x)^2))
%o A376809 (PARI) a(n) = sum(k=0, n\3, binomial(2*k,k) * binomial(n-k-1,n-3*k));
%Y A376809 Partial sums are A098479.
%Y A376809 Cf. A025178, A110170.
%K A376809 nonn,easy
%O A376809 0,4
%A A376809 _Seiichi Manyama_, Oct 04 2024