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 A373544 #20 Jun 11 2024 08:30:46
%S A373544 1,1,1,1,7,13,19,70,157,280,799,1894,3781,9646,23080,49159,119203,
%T A373544 283972,627760,1487095,3518617,7945561,18620746,43801447,100117099,
%U A373544 233475802,546859390,1258634440,2928668632,6839770279,15804569341,36739434904,85640217781,198337427839
%N A373544 Expansion of 1/(1 - x/(1 - 9*x^3)^(2/3)).
%F A373544 a(n) = Sum_{k=0..floor(n/3)} 9^k * binomial(2*n/3-k-1,k).
%F A373544 a(n) == 1 (mod 3).
%o A373544 (PARI) a(n) = sum(k=0, n\3, 9^k*binomial(2*n/3-k-1, k));
%Y A373544 Cf. A362210, A373543.
%Y A373544 Cf. A371458.
%K A373544 nonn
%O A373544 0,5
%A A373544 _Seiichi Manyama_, Jun 09 2024