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 A373543 #21 Jun 11 2024 08:30:50
%S A373543 1,1,1,7,13,64,151,634,1693,6514,18688,68239,204631,722920,2230498,
%T A373543 7711216,24246229,82612189,263112874,887565955,2852058448,9553983613,
%U A373543 30892668295,102975387211,334454025715,1110899344549,3619669508056,11992016509234,39164977065622
%N A373543 Expansion of 1/(1 - x/(1 - 9*x^2)^(2/3)).
%F A373543 a(n) = Sum_{k=0..floor(n/2)} 9^k * binomial(2*n/3-k/3-1,k).
%F A373543 a(n) == 1 (mod 3).
%o A373543 (PARI) a(n) = sum(k=0, n\2, 9^k*binomial(2*n/3-k/3-1, k));
%Y A373543 Cf. A362210, A373544.
%Y A373543 Cf. A371456.
%K A373543 nonn
%O A373543 0,4
%A A373543 _Seiichi Manyama_, Jun 09 2024