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 A371854 #7 Apr 09 2024 09:48:05
%S A371854 1,4,15,57,219,847,3290,12819,50066,195909,767790,3013002,11837043,
%T A371854 46548919,183209125,721628692,2844297119,11217639757,44265835891,
%U A371854 174765349896,690308413773,2727823240762,10783518961394,42644560775835,168699835910561,667580653569309
%N A371854 a(n) = Sum_{k=0..floor(n/3)} binomial(2*n-k+2,n-3*k).
%F A371854 a(n) = [x^n] 1/(((1-x)^2-x^3) * (1-x)^(n+1)).
%o A371854 (PARI) a(n) = sum(k=0, n\3, binomial(2*n-k+2, n-3*k));
%Y A371854 Cf. A002450, A105872, A371842.
%Y A371854 Cf. A360150, A371773.
%K A371854 nonn
%O A371854 0,2
%A A371854 _Seiichi Manyama_, Apr 09 2024