The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #5 Oct 22 2024 08:00:40
%S 1,-6,27,126,513,1296,-1782,-35964,-68526,2131110,31341168,257694210,
%T 1423944765,4790619126,5675652099,61932520134,2351897164665,
%U 36303263670942,365306247890865,2733496597694394,16050141707838840,82517222301874110,544262710381797330
%N Expansion of (1 - 9*x*(1 - 9*x)^(2/3))^(2/3).
%F a(n) = 9^n * Sum_{k=0..n} (-1)^k * binomial(2/3,k) * binomial(n-5*k/3-1,n-k).
%o (PARI) a(n) = 9^n*sum(k=0, n, (-1)^k*binomial(2/3, k)*binomial(n-5*k/3-1, n-k));
%Y Cf. A377244.
%K sign
%O 0,2
%A _Seiichi Manyama_, Oct 22 2024