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 A364641 #22 Aug 01 2023 09:33:28
%S A364641 1,1,1,2,3,5,10,16,31,59,101,206,376,692,1408,2528,4943,9767,17755,
%T A364641 35950,68659,129029,262758,490832,958948,1920580,3581020,7203080,
%U A364641 14054600,26665160,54195040,103450560,201749935,406617695,769870535,1539785150,3042812185
%N A364641 G.f. satisfies A(x) = 1/(1 - 2*x) - x*A(x)^3.
%H A364641 Seiichi Manyama, <a href="/A364641/b364641.txt">Table of n, a(n) for n = 0..1000</a>
%F A364641 a(n) = Sum_{k=0..n} (-1)^k * 2^(n-k) * binomial(n+k,2*k) * binomial(3*k,k) / (2*k+1).
%o A364641 (PARI) a(n) = sum(k=0, n, (-1)^k*2^(n-k)*binomial(n+k, 2*k)*binomial(3*k, k)/(2*k+1));
%Y A364641 Cf. A364645, A364646, A364647.
%Y A364641 Cf. A001405, A349253, A349255, A349533.
%K A364641 nonn
%O A364641 0,4
%A A364641 _Seiichi Manyama_, Jul 31 2023